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A clinical trial of different implant neck designs and immediate loading

L aurens den Hartog

Single-tooth

impl ants in the aesthetic

zone

Single-tooth implants in the aesthetic zone

A clinical trial of different implant neck designsand immediate loading

rijksuniversiteit groningen

Single-tooth implants in the aesthetic zone

A clinical trial of different implant neck designs and immediate loading

Proefschrift

ter verkrijging van het doctoraat in deMedische Wetenschappen

aan de Rijksuniversiteit Groningenop gezag van de

Rector Magnificus, dr. F. Zwarts,in het openbaar te verdedigen op

woensdag 26 januari 2011om 16.15 uur

door

Laurens den Hartog

geboren op 9 september 1980te Steenwijk

The research presented in this thesis was performed at the Department of Oral

and Maxillofacial Surgery, University Medical Center Groningen, The Nether-

lands.

This research project was supported by:

Nobel Biocare; study contract: Single tooth replacements with dental implants

in the aesthetic zone (Study number 2004-288)

Oral-maxillofacial Reconstructive and Implant Surgery related Research

Foundation (ORIS Research Foundation)

Publication of this thesis was supported by:

Tandtechnisch en Maxillofaciaal Laboratorium Gerrit van Dijk

E.S. Healthcare NV (www.isus.be)

Biomet 3i Netherlands BV (www.biomet3i.nl)

Dentsply Friadent Benelux NV (www.dentsply-friadent.nl)

Nobel Biocare Nederland BV (www.nobelbiocare.nl)

Straumann BV (www.straumann.nl)

Dent-Med Materials BV (Geistlich Bio-Oss®, Geistlich Bio-Gide®)

(www.dent-medmaterials.nl)

Nederlandse Vereniging voor Orale Implantologie (www.nvoi.nl)

Nederlandse Maatschappij tot bevordering der Tandheelkunde (www.nmt.nl)

Nederlandse Vereniging voor Gnathologie en Prothetische Tandheelkunde

(www.nvgpt.nl)

Nederlandse Vereniging voor Mondziekten, Kaak- en

Aangezichtschirurgie (www.nvmka.nl)

Dental Union (www.dentalunion.nl)

Van Velthuysen Liebrecht, financiele dienstverleners

(www.velthuysen.nl)

University of Groningen (www.rug.nl)

Lay-out & Cover: Saar de Vries

Printing: Drukkerij van der eems Heerenveen

Publisher: Laurens den Hartog, Groningen

ISBN: 978-90-367-4759-2

©Laurens den Hartog, 2010

All rights reserved. No part of this publication may be reported or transmitted, in

any form or by any means, without prior permission of the author.

Promotores: Prof. dr. G.M. Raghoebar

Prof. dr. H.J.A. Meijer

Prof. dr. A. Vissink

Beoordelingscommissie: Prof. dr. G.J. Meijer

Prof. dr. E. Rompen

Prof. dr. D. Wismeijer

Paranimfen: Drs. H.J. Santing

Dr. N. Tymstra

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1.Introduction

Among people, there are many opinions about the contribution of teeth to aes-

thetic appearance. This is illustrated in a recent newspaper article (Blandy 2009)

in which a popular phenomenon was described among some youngsters in Cape

Town, South Africa, in whom their healthy incisors had been extracted as fashion

statement:

“The laughing young man has a perfect set of teeth…..Suddenly he pops out a

pair of dentures, revealing a gap-toothed smile, a common sight among mixed-

race Capetonians that has spawned outrageous myths and stereotypes. […] “It

is fashion, everyone has it,” said 21-year-old Yazeed Adams, who insists he had

to take out his healthy incisors because they were “huge”. Ronald de Villiers, 45:

“my 11 year-old and 14 year-old had already had their teeth out “to look a bit pret-

tier”…..

In contrast to this phenomenon, in Western world, a missing anterior tooth is

not considered as being an image of beauty and might have a serious impact on

the individual’s life. Usually, these individuels have a strong wish for a prosthetic

replacement to rehabilitate function and aesthetics.

Dental implants have conquered a prominent role in contemporary dentistry

when it comes to single-tooth replacements. Excellent long-term survival rates

(Scheller et al. 1998, Romeo et al. 2002), psychological benefits for the patient

and tooth structure conservation, attribute to the growing popularity of dental

implants at the cost of conventional bridgework, resin-bonded restorations and

removable partial dentures. When primarily the focus was on survival of the im-

plant, currently creation of a high quality restoration for the long-term, satisfying

the criteria that reflect function and aesthetics is the ultimate ambition, particu-

larly in aesthetically delicate areas.

It is accepted that after implant placement and through time of function, im-

plants will display some extent of bone loss (Albrektsson et al. 1986, Laurell &

Lundgren 2009). However, peri-implant marginal bone loss should be limited,

since bone loss may induce pocket formation, which could be unfavorable for

long-term health of the peri-implant tissues (Rams et al. 1984, Heydenrijk et al.

2002). From an aesthetic point of view, it is also important to minimize marginal

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bone loss. Namely, the level of the peri-implant marginal bone is strongly related

to the level of the peri-implant mucosa (Bengazi et al. 1996, Hermann et al. 1997,

Chang et al. 1999, Hermann et al. 2000, Hermann et al. 2001). Loss of marginal

bone might therefore affect the level of the peri-implant mucosa, which, in turn,

is commonly considered as a major factor determining the aesthetic outcome

(Furhauser et al. 2005, Meijer et al. 2005).

There is evidence that the design of the implant neck influences the extent

of marginal peri-implant bone loss (Shin et al. 2006, Lee et al. 2007, McAllister

2007, Bratu et al. 2009, Nickenig et al. 2009). Although the traditional smooth

implant neck is accompanied by the least accumulation of plaque (Teughels

et al. 2006, Baldi et al. 2009), several studies found that a rough-surfaced im-

plant neck was accompanied by a significant reduction of marginal bone loss

when compared with a smooth implant neck (Shin et al. 2006, Bratu et al. 2009,

Nickenig et al. 2009). It has been suggested that an increase in implant surface

roughness improves bone integration in terms of the quantity and quality of bone

formation at the implant-bone interface (Cooper 2000). It is likely that, when

incorporated in the implant neck, these rough surface qualities are responsible

for reducing marginal bone loss. Furthermore, it has been reported that retention

elements at the implant neck, such as grooves or microthreads, favor the pres-

ervation of marginal bone (Palmer et al. 2000, Shin et al. 2006, Lee et al. 2007).

It is believed that these microthreads bring about a major decrease in interfacial

shear stress on the cortical bone, resulting in less marginal bone loss (Hansson

1999). In addition to the surface characteristics of the implant neck, it has been

suggested that a scalloped implant platform might preserve proximal marginal

bone (Wohrle 2003, Kan et al. 2007, McAllister 2007). This hypothesis was based

on the thought that a scalloped implant neck mirrors the natural alveolar ridge

curvature, particularly in the anterior zone, and consequently a more non-violent

position of the implant-abutment interface can be realized compared to common

flat platform implant designs.

Apart from the role of the implant neck design, the concept of immediate

loading has gained attention in contemporary implantology. This concept is de-

fined as the application of a load by means of a restoration within 48 hours after

implant placement (Laney 2007) and deviates from the conventional load-free

healing period of several months. Patients in need for an anterior single-tooth

replacement may benefit from immediate loading. Placement of the (provisional)

implant crown immediately after implant placement reduces overall treatment

time, avoids a second-stage operation and offers immediate oral comfort as there

is no need for a provisional removable prosthesis during the healing phase. Fur-

thermore, it has been hypothesized that immediate loading might be advanta-

geous for the appearance of the peri-implant soft tissue, since healing occurs

against a natural form immediately after implant surgery (Glauser et al. 2006).

Besides the beneficial effects of immediate loading, this loading concept has also

some inherent thought disadvantages. Amongst others, immediate loading may

induce micromotion and instability of the implant (Gapski et al. 2003, Trisi et al.

2009). Next, implant instability may result in fibrous encapsulation of the im-

plant and failing osseointegration (Lioubavina-Hack et al. 2006).

There is, however, a paucity of well-designed trials addressing the effect of

the implant neck design on bone and soft tissue parameters. Furthermore, the

aesthetic outcome and patient satisfaction are underexposed in anterior single

implant research (Belser et al. 2004). The same shortcomings apply to trials in-

vestigating immediate implant loading as being a reliable strategy to replace an

anterior tooth (Gapski et al. 2003). To gain more insight into the questions raised

in this and the previous paragraphs, the general aims of this thesis were:

to compare the treatment outcome of single-tooth implants with different - neck designs placed in the maxillary aesthetic zone;

to compare the treatment outcome of immediate loading with conventional - loading of single-tooth implants placed in the maxillary aesthetic zone.

The specific aims of this thesis were:

to review systematically the literature regarding the efficacy of single implant - therapy in the aesthetic zone (Chapter 2);

to compare the marginal bone level change and clinical outcome of implants - with a 1.5 mm smooth neck, a rough neck with grooves and a scalloped

rough neck with grooves used for single-tooth replacements in the maxillary

aesthetic region (Chapter 3);

to evaluate the aesthetic outcome of the above mentioned implant neck de-- signs from a professional’s and patient’s perception (Chapter 4);

to compare immediate loading with conventional loading of single-tooth - implants in the aesthetic zone for marginal bone level change, clinical and

aesthetic outcome and patient satisfaction (Chapter 5).

The immediate loading protocol of our study is illustrated in a detailed clinical

report (Chapter 6). Furthermore, a chapter is devoted to how to treat a trauma to

an anterior implant crown (Chapter 7).

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This chapter is an edited version of the manuscript: Den Hartog, L., Huddleston Slater J.J., Vissink,

A., Meijer, H.J., Raghoebar, G.M. Treatment outcome of immediate, early and conventional single-

tooth implants in the aesthetic zone. A systematic review to survival, bone level, soft tissue, aesthetics

and patient satisfaction. Journal of Clinical Periodontology 2008; 35: 1073 - 1086

2.

Treatment outcome of immediate, early and

conventional single-tooth implants in the aesthetic

zone

A systematic review to survival, bone level, soft tissue, aesthetics and patient satisfaction

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AbstrAct

Aim: To evaluate, through a systematic review of the literature, the out-

come of single-tooth implants in the aesthetic zone with natural adjacent

teeth, thereby addressing immediate, early and conventional implant ap-

proaches.

Material and Methods: MEDLINE (1950-2008), EMBASE (1966-2008), and

CENTRAL (1800-2008) were searched to identify eligible studies. Two re-

viewers independently assessed the methodological quality using specific

study-design related assessment forms.

Results: Out of 86 primarily selected articles, 19 studies fulfilled the inclu-

sion criteria. A meta-analysis showed an overall survival rate of 95.5% (95%

CI: [93.0 – 97.1]) after one year. A stratified meta-analysis revealed no differ-

ences in survival between immediate, early and conventional implant strat-

egies. Minor marginal peri-implant bone resorption was found together

with low incidence of biological and technical complications. No significant

differences in outcome measures were reported in clinical trials comparing

immediate, early or conventional implant strategies.

Conclusion: The included literature suggest that promising short-term re-

sults can be achieved for immediate, early and conventional single-tooth

implants in the aesthetic zone. However, important parameters as aesthetic

outcome, soft tissue aspects and patient satisfaction were clearly underex-

posed. The question whether immediate and early single implant therapies

will result in better treatment outcomes remains inconclusive due to lack

of well-designed controlled clinical studies.

IntroductIon

The application of dental implants for single-tooth replacements has evolved into

a viable prosthodontic alternative to conventional fixed bridgework, resin-bonded

restorations or removable partial dentures. Long-term studies have reported ex-

cellent implant survival rates when applied for single-tooth replacements (Schel-

ler et al. 1998, Romeo et al. 2002). Psychological benefits and tooth structure

conservation adjacent to the tooth to be replaced, are among the advantages of

implant supported restorations.

In the anterior zone, the success of single-tooth implant therapy is not only

determined by high survival rates, but even more by the (long-term) quality of

survival, dictated by a mixture of several factors. Preferably, the appearance of

the peri-implant soft tissue should be in harmony with the mucosa around the

adjacent teeth and the implant crown should be in balance with the neighbouring

dentition (Meijer et al. 2005). Various implant treatment strategies have been pro-

posed for the accomplishment of optimal aesthetics. These include approaches to

rehabilitate the underlying bone structures by augmentation procedures with au-

tologous bone and/or bone substitutes (Weber et al. 1997, Jensen et al. 2006, Pelo

et al. 2007), techniques to manipulate and enhance the architecture of the peri-

implant soft tissue (Zetu & Wang 2005, Esposito et al. 2007) and methods for al-

veolar ridge preservation following tooth extraction (Lekovic et al. 1997, Irinakis &

Tabesh 2007). Furthermore, implants and abutments with specific configurations

have been introduced to sustain the hard and soft tissue (Wohrle 2003, Morton et

al. 2004, Lazzara & Porter 2006, Maeda et al. 2007, Noelken et al. 2007) together

with provisionalization techniques to restore the soft tissue contour (Jemt 1999,

Al-Harbi & Edgin 2007), and the introduction of ceramic customized abutments

and ceramic implant crowns (Canullo 2007, Schneider 2008).

Traditionally, dental implants were placed in healed extraction sites according

to a two-stage surgical procedure and an undisturbed load-free period of three

to six months. In contemporary implantology, however, installation of implants

in fresh extraction sockets and reducing the load-free period by immediate re-

storing implants after insertion have gained attention. Besides shortening of to-

tal treatment time, fewer surgical interventions and eliminating the need for a

temporary prosthesis, these immediate approaches might lead to a reduction of

peri-implant crestal bone loss and a better soft tissue healing thus possibly im-

proving the aesthetics (Esposito et al. 2006, Glauser et al. 2006, Harvey 2007).

On the other hand, there are potential risk factors involved with these techniques

such as enhanced possibility of infection, mismatch between socket wall and im-

plant leading to gap creation and induction of fibrous tissue formation around

the bone-implant interface caused by implant micromovement during eventful

wound healing (Gapski et al. 2003, Esposito et al. 2006). These risk factors may

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worsen the treatment outcome. This discrepancy needs further study.

The outcome of a single-tooth implant with natural neighbouring teeth may

be dissimilar to cases in which multiple adjacent teeth are replaced by dental im-

plants, because dimensions of the hard and soft tissue between adjacent implants

differ significantly from dimensions found in single implant cases. Single implant

cases take benefit of tissue support of the adjacent dentition (Grunder 2000, Kan

et al. 2003b, Belser et al. 2004). When considering the heights of inter-implant

papillae for instance, studies indicated that these papillae might show inadequacy

for complete enclosure of the inter-implant area with soft tissue, thereby failing to

duplicate the interproximal soft tissue appearance of the adjacent teeth (Tarnow

et al. 1992, Tarnow et al. 2003, Lee et al. 2005). This deficiency may affect the

aesthetic outcome unfavorably. The soft tissue height proximal to single-tooth

implants is on average higher and is suggested to be related to the interproximal

bone level of the adjacent teeth (Grunder 2000, Kan et al. 2003b). Hence, single-

tooth implant therapy may lead to more favorable treatment outcomes compared

to a therapy in which adjacent implants are involved.

To date, several reviews have been published regarding the clinical outcome of

immediate and conventional implant supported single-tooth restorations in par-

tially edentulous patients (Creugers et al. 2000, Berglundh et al. 2002, Belser et

al. 2004, Glauser et al. 2006, Jung et al. 2008). Most of these reviews have mainly

converged on implant survival and addressed to a lesser degree other outcome

measures that determine the quality of survival. Furthermore, none of these re-

views systematically analyzed the literature concerning the efficacy of single-tooth

implants in the aesthetic zone neither did these reviews concentrate explicitly

on the outcome of single implants with natural neighbouring teeth, applied to

replace one missing tooth. However, it is worthwhile for patients and clinicians

to know whether an immediate or conventional single-tooth implant represents

a predictive, reliable and effectual therapy to re-establish function and aesthetics

subsequent to the loss of a single anterior tooth. Therefore, the objective of this

study was to evaluate, through a systematic review of the literature, the outcome

of single-tooth replacements by dental implants in the aesthetic zone in cases in

which the adjacent teeth are natural, thereby focussing on immediate, early and

conventional implant treatment strategies.

MAterIAl And Methods

Types of studies Longitudinal studies (Randomized controlled trials (RCTs), clinical trials, cohort-

studies and case series) were considered for evaluation. Retrospective studies were

excluded. Only case series that investigated at least five patients were contemplated

for inclusion. No time restrictions were implemented. Language was restricted to

papers published in English, German, French, Spanish, Italian and Dutch.

Type of participantsPatients who were treated with an implant-retained single-tooth replacement in the

aesthetic zone neighbored with natural teeth, could be included. The aesthetic zone

was defined as the region in the maxilla or mandible, ranging from second premo-

lar to second premolar (teeth 15-25 and teeth 35-45).

Types of interventionimmediate implant placement: defined as implant placement immediately fol-- lowing extraction of a tooth;

early implant placement: defined as installation of the implant 4 to 8 weeks - after extraction;

conventional implant placement: implant placement ≥ 8 weeks post-extrac-- tion;

immediate loading: application of a load by means of a restoration within 48 - hours of implant placement;

early loading: application of a load by means of a restoration after 48 hours but - less than 3 months after implant placement;

conventional loading: application of a load by means of a restoration ≥ 3 - months after implant placement (Laney 2007).

For studies to be eligible in this review, they had to evaluate endosseous root-form

dental implants with a follow-up of at least 1 year after placement of the implant

crown.

Types of outcome measuresimplant survival, defined as presence of the implant at time of follow-up ex-- aminations;

changes in marginal peri-implant bone level assessed on radiographs;- aesthetics evaluated by dental professionals;- aspects of the peri-implant structures, i.e. level of marginal gingiva, papilla in-- dex (Jemt 1997), probing pocket depth, presence of plaque, bleeding on prob-

ing;

patient satisfaction including aesthetics;- biological and technical complications.-

Search StrategyFor this review, a thorough search of the literature was conducted in databases

of MEDLINE (1950-2008 (via PUBMED) and EMBASE (1966 – 2008). The search

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was supplemented with a systematic search in the ‘Cochrane Central Register

of Controlled Trials’ (CENTRAL) (1800–2008). The search strategy used, was a

combination of MeSH terms and free text words and is summarized in Table 1.

The search was complemented by checking references of relevant review arti-

cles and eligible studies for additional useful publications. Titles and abstracts of

the searches were scanned independently by two examiners. Full-text documents

were obtained for all possibly relevant articles. Full text analysis was performed

for second selection by two reviewers independently against the stated inclusion

criteria. In case of disagreement, consensus was reached by discussion, if neces-

sary in consultation with a third reviewer.

Table 1. Search strategy.

#1 Search “Dental Implants”[MeSH] OR “Dental Implantation”[MeSH] OR implant*

#2 Search “single implant*” OR “single tooth” OR “single teeth” OR “single crown*” OR

“single restoration*”

#3 Search “aesthetic*” OR “esthetic*” OR “anterior*” OR “front*” OR “incisor*”

#4 Search #1 AND #2 AND #3

Run data search: June 2008.

Quality assessmentMethodological quality was assessed using specific study-design related forms de-

signed by the Dutch Cochrane Collaboration. As there was no checklist available for

the assessment of the quality of case series, a quality-assessment tool was specifi-

cally developed for this review, adapted from the quality form used for clinical trials

(Table 2). Two observers independently generated a score for the included articles,

expressed in the number of plusses given. It was decided that studies scoring 5 or

more plusses were considered to be methodological ‘acceptable’.

Data extraction and synthesisFor each trial the following data were extracted by two review authors independ-

ently and recorded in a data sheet:

number of patients, implants placed, drop-outs and follow-up time. For all - included longitudinal studies of more than one year, follow-up time was cal-

culated as person-years;

details of type of intervention;- details of the outcomes stated, including method of assessment. -

Agreement was reached by a consensus discussion and if necessary a third

reviewer was consulted. If feasible, a meta-analysis was carried out if the outcome

measures could be meaningfully combined.

Table 2. Quality assessment of case series.

Item + - ?

1. Are the characteristics of the study group clearly described?

2. Is there a high risk of selection bias? Are the inclusion and exclusion criteria clearly described?

3. Is the intervention clearly described? Are all patients treated according to the same intervention?

4. Are the outcomes clearly described? Are adequate methods used to assess the outcome?

5. Is blinding used to assess the outcome?

6. Is there a sufficient follow-up?

7. Can selective loss-to follow-up sufficiently be excluded?

8. Are the most important confounders or prognostic factors identified and are these taken into consideration with respect to the study design and analysis?

Five or more plusses = methodologically acceptable.

Statistical analysisWith respect to the quality assessment, agreement between both reviewers was

calculated using Cohen’s kappa (κ) statistics.

For the meta-analysis the statistical software package “Meta-analysis” was

used (Comprehensive Meta-analysis Version 2.2, Biostat, Englewood NJ (2005),

www.meta-analysis.com). For the calculation of the overall effects for the included

studies, weighted rates together with random effects models were used. Stra-

tification procedures were applied for follow-up time and type of intervention.

Within each stratum, heterogeneity between included studies was checked by

human eyeball criteria.

results

Description of studiesThe MEDLINE search provided 610 hits, the EMBASE search 23 hits and the CEN-

TRAL search 27 hits. After scanning of titles and abstracts, 86 articles were select-

ed and screened as full text articles. Reference-checking of relevant reviews and

included studies revealed one additional article (Hall et al. 2006). However, this

report showed to be a shortened version of a later publication (Hall et al. 2007)

and did not contain any new information. A number of 41 studies did not satisfy

2

Cha

pter

Syst

emat

ic r

evie

w

2

20 2121

The κ-value for inter-assessor agreement on the methodological quality was 0.89.

Disagreements were generally caused by slight differences in interpretation and

were easily resolved in a consensus meeting. Finally, 19 publications remained for

data extraction. Figure 1 outlines the algorithm of the study selection procedure.

Of the included studies, 5 were RCTs, 2 were clinical trials and 12 were case series.

Six publications presented outcomes of the same patient population, but differed

in follow-up (Palmer et al. 1997, 2000, Cooper et al. 2001, 2007, Jemt & Lekholm

2003, 2005) and results of one study group were reported in two different publi-

cations addressing different topics (Schropp et al. 2005a, 2005b).

Identified articles- MEDLINE search: n = 610- EMASE search: n = 23- CENTRAL search: n = 27

Included for full text analysisn = 86

Included for methodological appraisaln = 26

Included for data analysisn = 19

Excluded articles• Improper study design• Non-topic related• No abstract available• Follow-up < 1 year

Excluded articles• Required data not presented• Improper study design• Follow-up < 1 year

Excluded articlesGrunder 2000; Groisman et al., 2003; Lorenzoni et al., 2003; Locante et al., 2004; Henriksson et al., 2004; Ferrara et al. , 2006; Barone et al., 2006

Most of the studies only evaluated maxillary implants, but three studies did

also include implants placed in the mandible (38 implants in total) (Schropp et

al. 2005a, Schropp et al. 2005b, Romeo et al. 2008). Furthermore, implants were

installed mostly in completely healed extraction sockets or early after extraction

(10 days to 4 weeks) and subsequently were restored according to immediate,

early (1 to 3 weeks after implant placement) or conventional loading protocols.

Restorations that were seated immediate or early after implant placement, were

the inclusion criteria because data of single-tooth implants in anterior and poste-

rior zones was not presented separately or adjacent implants were also included,

making it not possible to extract proper data. Furthermore, 14 studies were ex-

cluded due to improper study design (not longitudinal or not prospective) and 5

studies because of a follow-up < 1 year. A total of 26 articles fulfilled the inclusion

and exclusion criteria and were assessed methodologically. Of these 26 studies, 7

studies were excluded. Reasons for exclusion are depicted in Table 3.

Table 3. Studies excluded after quality assessment and reasons for exclusion.

Study Study design Reasons for exclusion

Henriksson 2004

Clinical trial Heterogeneity in clinical procedure (different im-plants, different load-free periods), in/exclusion criteria unclear, no blinding used, prognostic factors/confounders not considered.

Lorenzoni 2003

Case series Patients not treated according to same intervention (immediate and conventional placement included), in/exclusion criteria unclear, no blinding used, prognos-tic factors/confounders not considered.

Ferrara 2006 Case series High risk of selection bias (implants with insufficient primary stability were excluded; method to assess sta-bility not clear), outcomes not clearly described, meth-ods used to assess the outcome unclear, no blinding used, prognostic factors/confounders not considered.

Grunder 2000 Case series Patients characteristics unclear, in/exclusion criteria unclear, no blinding used, prognostic factors/con-founders not considered.

Locante 2004 Case series Patients not treated according to same intervention (immediate and conventional placement included), high risk of selection bias (implants with insufficient primary stability were excluded; method to assess stability not clear), in/exclusion criteria unclear, no adequate methods used to assess the outcome, no blinding used, follow-up routine unclear, prognostic factors/confounders not considered.

Groisman 2003

Case series Patient characteristics unclear, high risk of selection bias (only favorable cases selected), method of assess-ment not clear, no blinding used, prognostic factors/confounders not considered, follow-up routine unclear.

Barone 2006 Case series Patient characteristics not clear, high risk of selection bias (only favorable cases selected), no blinding used, prognostic factors/confounders not considered.

Figure 1. Algorithm of study selection procedure.

22 2323

Tab

le 4

. St

ud

y ch

arac

teri

stic

s an

d o

utc

om

es o

f in

clu

ded

stu

die

s, a

rran

ged

acc

ord

ing

to

typ

e o

f in

terv

enti

on

an

d s

tud

y d

esig

n.

Stud

yIn

terv

enti

onD

esig

nN

o. o

f pa

tien

ts/

impl

ants

Impl

ant

syst

emR

easo

n(s

) for

too

thlo

ss (n

o.)

Follo

w-

up p

erio

d (y

rs)

No.

of

impl

ant

drop

-ou

ts**

Surv

ival

ra

te (%

)C

han

ge in

mar

-gi

nal

bon

e le

vel

± SD

(mm

)

Kan

20

03

Imm

edia

te p

lace

men

t an

d im

med

iate

load

ing

CS

35/3

5R

epla

ce

Sele

ctF

ract

ure

(15)

, en

dodo

nti

c fa

ilure

(12)

, roo

t res

orp-

tion

(8)

10

100

- 0.2

4 ±

0.3

5* #

De

Rou

ck 2

00

8Im

med

iate

pla

cem

ent

and

imm

edia

te lo

adin

gC

S30

/30

Rep

lace

Se

lect

Fra

ctu

re (1

0),

cari

es/

endo

don

tic

(9),

peri

-od

onta

l (7)

, ro

ot r

esor

ptio

n (4

)

11

97

- 0.8

8 ±

0.5

2* #

Lin

debo

om 2

00

6Im

med

iate

pla

cem

ent v

s co

nve

nti

onal

pla

cem

ent

RC

T

T C25

/25

25/2

5F

rial

it-2

N

R1

2 09

210

0- 0

.51

± 0

.12*

#

- 0.5

2 ±

0.1

5* #

Sch

ropp

20

05

(a)

Ear

ly p

lace

men

t vs

con

ven

tion

al p

lace

men

tR

CT

T C

23/2

322

/22

3iR

oot f

ract

ure

(NR

), en

dodo

nti

c fa

ilure

(NR

), pe

riod

onti

tis

(NR

), ad

van

ced

cari

es le

sion

s (N

R)

2N

RN

RN

R

Sch

ropp

20

05

(b)

Ear

ly p

lace

men

t vs

con

ven

tion

al p

lace

men

tR

CT

T C

23/2

323

/23

3iR

oot f

ract

ure

(NR

), en

dodo

nti

c fa

ilure

(NR

), pe

riod

onti

tis

(NR

), ad

van

ced

cari

es le

sion

s (N

R)

23 2

91

96

- 0.8

± N

R ‡

- 0.7

± N

R ‡

Got

fred

sen

20

04

Ear

ly p

lace

men

t vs

con

ven

tion

al p

lace

men

tC

T

T C

10/1

010

/10

Ast

ra T

ech

Roo

t fra

ctu

re (1

5), a

gen

-es

is (3

), tr

aum

a (2

)5

0 010

010

0- 0

.34

± 0

.57 ¶

- 0.2

6 ±

0.3

8 ¶

Rom

eo 2

00

8Im

med

iate

pla

cem

ent

CS

48/4

8IT

IC

arie

s/en

dodo

nti

c w

ith

ro

ot o

r cr

own

fra

ctu

re

(NR

)

10

100

NR

Tab

le 4

. (C

on

tin

ued

)

Stud

yIn

terv

enti

onD

esig

nN

o. o

f pa

tien

ts/

impl

ants

Impl

ant

syst

emR

easo

n(s

) for

too

thlo

ss (n

o.)

Follo

w-

up p

erio

d (y

rs)

No.

of

impl

ant

drop

-ou

ts**

Surv

ival

ra

te (%

)C

han

ge in

mar

-gi

nal

bon

e le

vel

± SD

(mm

)

Hal

l 20

07

Imm

edia

te lo

adin

g vs

co

nve

nti

onal

load

ing

RC

T

T C14

/14

14/1

4So

uth

ern

Im

plan

tsN

R1

1 29

310

0- 0

.63

± 1

.00

¶

- 0.7

8 ±

1.0

1 ¶

Eri

csso

n 2

00

0Im

med

iate

load

ing

vs

con

ven

tion

al lo

adin

gC

T

T C

14/1

48/

8B

rån

emar

kN

R1.

52 0

85.7

100

- 0.1

4 ±

0.3

6 ¶

- 0.0

7 ±

0.7

9 ¶

Coo

per

200

1E

arly

load

ing

CS

48/5

4A

stra

Tec

hN

R1

39

4.4

- 0.4

± N

R §

Coo

per

200

7E

arly

load

ing

CS

48/5

4A

stra

Tec

hN

R3

119

4.4

-0.4

2 ±

0.5

9§

An

ders

en 2

00

2E

arly

load

ing

CS

8/8

ITI

NR

50

100

+ 0

.53

± N

R§

Mei

jnde

rt 2

00

7C

onve

nti

onal

RC

T9

3/9

3IT

IN

R1

29

7.8

NR

Jem

t 20

03

Con

ven

tion

alC

S10

/10

Brå

nem

ark

Tra

um

a (1

0)

31

100

- 0.3

± 0

.36

¶

Jem

t 20

05

Con

ven

tion

alC

S10

/10

Brå

nem

ark

Tra

um

a (1

0)

62

100

- 0.3

± 0

.24 ¶

Zar

one

200

6C

onve

nti

onal

CS

30/3

4IT

IA

gen

esis

(30

)2

- 3.2

110

0- 1

.2 ±

0.6

1 §

Pal

mer

19

97

Con

ven

tion

al

CS

15/1

5A

stra

Tec

h

NR

21

100

+ 0

.01

± 0

.50

* ¶

Pal

mer

20

00

Con

ven

tion

alC

S15

/15

Ast

ra T

ech

NR

51

100

+ 0

.12

± 0

.49

* ¶

Car

daro

poli

20

06

Con

ven

tion

alC

S16

/16

Brå

nem

ark

NR

15

100

- 1.6

± 0

.57*

#

*Sta

nda

rd d

evia

tion

cal

cula

ted.

**

Defi

ned

as

impl

ants

that

did

not

su

rviv

e an

d im

plan

ts lo

st to

fol

low

-up.

# F

rom

impl

ant p

lace

men

t. ‡

Fro

m h

ealin

g ab

utm

ent p

lace

men

t. §F

rom

tem

-

pora

ry c

row

n p

lace

men

t. ¶

Fro

m d

efin

itiv

e cr

own

pla

cem

ent.

Abb

revi

atio

ns:

NR

= n

ot r

epor

ted,

RC

T=r

ando

miz

ed c

linic

al tr

ial,

CT

= cl

inic

al tr

ial,

CS

= ca

se s

erie

s, T

= te

st g

rou

p,

C =

con

trol

gro

up.

24 2525

Tab

le 5

. O

utc

om

es o

f in

clu

ded

stu

die

s, a

rran

ged

acc

ord

ing

to

typ

e o

f in

terv

enti

on

an

d s

tud

y d

esig

n.

Stud

yA

esth

etic

s

(ran

ge)

Pat

ien

t sa

tisf

acti

on

(ran

ge)

Pap

illa

in

dex

Leve

l of

mar

-gi

nal

gin

giva

±

SD (m

m)

Pro

bin

g de

pth

± SD

(m

m)

Pre

sen

ce

of p

laqu

eB

leed

ing

on

prob

ing

Com

plic

atio

ns

Kan

20

03

NR

9.9

(9 -

10)

NR

-0

.55

± 0

.53

‡N

R

26%

N

R

4 fi

stu

la, 2

tem

pora

ry

abu

tmen

ts lo

osen

ed

De

Rou

ck 2

00

8N

R9

.3 (8

.2-1

0)

NR

-0.5

3 ±

0.7

6 ‡

3.46

± 0

.69

17%

41%

1 cr

own

loos

ened

Lin

debo

om 2

00

6T C

NR

NR

22

% s

core

2, 7

8%

scor

e 3

28%

sco

re 2

, 72%

sc

ore

3

61%

pro

per

leve

l84

% p

rope

r le

vel

NR

N

R

NR

NR

Sch

ropp

20

05

(a)

T C

NR

N

R

resp

. 8%

,35%

,57%

sc

ore

0,1

,2 *

resp

. 3%

,34%

,63%

sc

ore

0,1

,2 *

83%

pro

per

leve

l

50%

pro

per

leve

l

NR

NR

N

RN

R

Sch

ropp

20

05

(b)

T CN

R

NR

N

RN

R4.

2 ±

1.4

#4.

1 ±

1.1

#N

R

NR

1 fi

stu

la, e

xpos

ure

of

met

al m

argi

ns

in 4

ca

ses

Got

fred

sen

20

04

T

C5.

9 (2

.9 -

9.5

)8.

4 (6

.1 -

9.7

)9

.6 (7

.1 -

10)†

9.1

(5.1

- 10

)†

NR

- 0

.3 ±

0.5

¶

+ 0

.3 ±

0.6

¶

NR

21

% (p

oole

d da

ta)

38%

(poo

led

data

)2

soft

tiss

ue

deh

is-

cen

ces,

1 fi

stu

la, 2

ab

utm

ents

loos

ened

Rom

eo 2

00

8N

RN

R6

7% s

core

3 *

NR

NR

NR

NR

No

com

plic

atio

ns

Hal

l 20

07

T CN

RN

R

resp

. 18%

,51%

,31%

sc

ore

1,2,

3 (p

oole

d da

ta) N

o si

gn. d

iffs

.

-0.6

7 ±

0.4

9 §

-0.3

3 ±

0.7

8 §

No

sign

. di

ffs.

No

sign

. di

ffs.

N

o si

gn.

diff

s.1

tem

pora

ry c

row

n

frac

ture

d

Eri

csso

n 2

00

0T C

NR

A

ll pa

tien

ts

sati

sfied

All

pati

ents

sa

tisfi

ed

NR

N

RN

R

25%

25%

17%

25%

1 te

mpo

rary

cro

wn

lo

osen

ed tw

ice

Tab

le 5

. (C

on

tin

ued

)

Coo

per

200

1N

R

NR

N

R

+ 0

.34

± 0

.94

§N

R

0.5

% o

f si

tes

exam

ined

NR

1 ad

jace

nt t

ooth

mi-

grat

ed, 1

per

i-im

plan

t m

uco

siti

s, 1

impl

ant

disc

omfo

rt, 3

cro

wn

s lo

osen

ed; 4

fra

ctu

red

Coo

per

200

7N

RN

RN

R+

0.5

1 ±

1.4

2 §

NR

NR

NR

See

abov

e. N

o n

ew

com

plic

atio

ns

re-

port

ed

An

ders

en 2

00

2N

RN

RN

RN

RN

RN

RN

R1

fist

ula

, 3 c

row

ns

loos

ened

Mei

jnde

rt 2

00

76

6%

acc

epta

ble

8.5

( 6-1

0)

NR

N

RN

R

NR

N

R

NR

Jem

t 20

03

NR

N

R

50%

sco

re 2

, 50

%

scor

e 3

NR

N

R

NR

NR

No

com

plic

atio

ns

Jem

t 20

05

NR

NR

NR

- 0.1

± N

R ¶

NR

NR

NR

No

com

plic

atio

ns

Zar

one

200

63%

not

sat

isfa

ctor

y N

R

resp

. 6%

,12%

,82%

sc

ore

1,2,

3-0

.6 ±

NR

§2.

6 ±

0.2

#18

%

No

blee

din

gN

o im

plan

t-re

late

d co

mpl

icat

ion

s.

Pal

mer

19

97

NR

NR

NR

No

rece

ssio

nN

RN

RN

o bl

eedi

ng

No

soft

tiss

ue

com

-pl

icat

ion

s. 1

cro

wn

lo

osen

ed,

1 po

rcel

ain

fra

ctu

re

Pal

mer

20

00

NR

NR

NR

N

o re

cess

ion

NR

N

RR

are

See

abov

e. N

o n

ew

com

plic

atio

ns

re-

port

ed

Car

daro

poli

20

06

NR

NR

resp

. 14%

,68%

,18%

sc

ore

1,2,

3 -0

.6 ±

0.7

¶2.

4 ±

0.8

NR

9%

N

R

*Mod

ifica

tion

of

Pap

illa

Inde

x. †

Mea

n V

AS-

scor

es f

or a

esth

etic

app

eara

nce

an

d ge

ner

al f

un

ctio

n. #

Stan

dard

dev

iati

on c

alcu

late

d. ‡

Fro

m im

plan

t pla

cem

ent.

§ Fro

m te

mpo

rary

cro

wn

plac

emen

t. ¶

Fro

m d

efin

itiv

e cr

own

pla

cem

ent.

Abb

revi

atio

ns:

T=t

est g

rou

p, C

= c

ontr

ol g

rou

p, N

R =

not

rep

orte

d.

2

Cha

pter

Syst

emat

ic r

evie

w

2

26 2727

all kept out of direct occlusal contact. Two studies reported on immediately re-

stored implants placed directly after tooth extraction. All clinical trials except one

compared the outcome of immediate or early implant placement and immediate

or early implant loading with conventional approaches. This RCT focused on dif-

ferent bone augmentation procedures and all implants were placed and restored

conventionally according to the same protocol (Meijndert et al. 2007). Character-

istics of the included studies are presented in Table 4 and are arranged according

to type of intervention and study design.

Due to methodological diversity of the ‘acceptable’ studies, only data on implant

survival and to a limited degree marginal bone resorption could be meaningfully

combined in a meta- analysis. Therefore, the outcomes are mainly presented as a

descriptive review in the subsequent sections and are depicted in Table 4 and 5.

Implant survival The implant survival rate was defined as the percentage of implants that was still

present at follow-up. All implants that were lost, failed within the first six months

after placement. In some studies implant mobility was detected at second stage

surgery (seven implants) (Schropp et al. 2005b, Lindeboom et al. 2006, Meijndert

et al. 2007) or occurred following placement of the provisional restoration (one

implant) (Cooper et al. 2001), whereas other implants were already in function

when they appeared not to be osseointegrated (six implants) (Ericsson et al.

2000, Cooper et al. 2001, Hall et al. 2006, De Rouck et al. 2008). Altogether, a

total number of 509 single-tooth implants was originally installed in 499 patients

of which 13 patients and 13 implants were lost to follow-up and no information

on survival was available regarding these implants. A total of 14 implants did not

survive.

Since it is generally known that implant loss is most often observed early after

implant installation and/or implant restoration, event rates and survival rates were

calculated in a stratified manner. To that end, results are presented for implants

that were followed up to one year after implant restoration (including implants

that were lost before restoration and consequently were not yet in function) and

implants with an observation period of more than one year after restoration (with

a correction for implants that were lost within the first year after restoration). Re-

sults of the weighted meta-analysis (for study size) of implant loss within one year,

expressed as event rates, are shown in Figure 2. The overall event rate was calcu-

lated as 0.045 (95% conficende interval (CI): 0.029 – 0.070) and can be expressed

as a survival rate of 95.5% (95% CI: 93.0 – 97.1). The weighted meta-analysis (for

person-years and study-size) regarding loss of implants that are more than one

year in function, showed an event rate of 0.007 (95% CI: 0.003 – 0.019).

Globally four different treatment strategies could be identified. In this matter,

survival outcomes of immediate and early placed implants that were restored

conventionally were combined as well as implants that were installed convention-

ally but were restored immediately or early. Results of the weighted (for study-

size) stratified meta-analysis are presented in Table 6, revealing no differences

in survival rate after one-year follow-up. Focussing on the studies individually, no

statistically significant differences in implant survival were found in clinical trials

comparing immediate or early implant procedures with conventional ones.

Figure 2. Meta-analysis of implant loss within one year after restoration.

2

Cha

pter

Syst

emat

ic r

evie

w

2

28 29

Marginal bone level changesAll articles except three reported on changes in marginal peri-implant bone levels

determined radiographically. Most of the studies used intra-oral radiographs ob-

tained according to a standardized paralleling technique, although it was ques-

tionable whether Cooper et al. (2001), Jemt and Lekholm (2003, 2005), Palmer et

al. (1997, 2000) and Gotfredsen (2004) used standardized radiography for their

measurements. There was variety in the peri-implant bone level evaluation over

time since studies used different starting points for their analysis. In the various

studies, the first radiographic examinations had been performed just after im-

plant placement, after healing abutment connection, at provisional crown place-

ment or at definitive crown placement. Because of this heterogeneity, it was not

possible to perform an analysis from which conclusions could be drawn concern-

ing differences in marginal bone changes between the several treatment strate-

gies. However, some insight could be gained into crestal bone changes occurring

from definitive crown placement to one year thereafter in patients treated conven-

tionally. The five studies included for this weighted (for study-size) meta-analysis

(viz. Palmer et al. 1997, Ericsson et al. 2000, Gotfredsen 2004, Jemt & Lekholm

2005, Cardaropoli et al. 2006) (in total 52 implants) revealed a mean marginal

bone loss of 0.20 mm (95% CI: 0.034 – 0.36) during the first year after installa-

tion of the definitive crown (see Figure 3). Data from radiographic examinations

were mostly presented as mean values and consequently no frequency distribu-

tions were given. Cooper et al. (2001) considered the incidence of marginal bone

loss of 48 implants one year after insertion. The latter authors found that after

one year eight implants showed a cortical bone loss of 1.0 to 2.0 mm and three

implants more than 2.0 mm. Finally, the bone level changes detected in the ex-

perimental and conventional study groups of the included clinical trials were not

significantly different.

Table 6. Stratified meta-analysis of implant survival after one-year.

Intervention No. of patients/ implants

No. of studies

included

No. of implants

lost to follow-up*

No. of implants that not survived

Calculated survival rate (%) [95% CI]

Immediate place-ment and immediate loading

65/65 2 1 1 97.5 [88.3 - 99.5]

Immediate/early placement, conven-tional loading

106/106 4 1 4 93.6 [85.4 - 97.3]

Conventional placement, immediate/early loading

84/90 4 0 6 92.4 [84.4 - 96.4]

Conventional placement, conventional loading

244/248 11 11 3 96.8 [85.7 - 97.2]

* These implants were not included in the analysis.

Abbreviations: CI=convidence interval.

* * *

Figure 3. Meta-analysis of marginal bone level changes 1 year after instal-lation of the definitive crown.

AestheticsAlbeit all implants reviewed were inserted in the aesthetic zone, only three stud-

ies included the aesthetic outcome in their analysis. Zarone et al. (2006) con-

sidered one implant not being satisfactory because of exposure of the titanium

neck. It was, however, unclear how the aesthetics were measured. At the three-

year control visit Gotfredsen (2004) asked an independent dentist to evaluate

the aesthetic appearance of the implant crowns using a visual analog scale (VAS)

ranging from ‘very unsatisfied’ (score 0) to ‘very satisfied’ (score 10). In the study

by Meijndert et al. (2007), a prosthodontist rated the aesthetics on colour pho-

tographs using an objective rating index. It appeared that 34% of the cases were

judged as poor aesthetics.

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Peri-implant structuresTo evaluate the quantity of the interproximal gingival papillae, some studies made

use of the papilla index according to Jemt (1997) or a slight modification of this

classification (Schropp et al. 2005a, Romeo et al. 2008). It revealed that in these

studies an increase of tissue volume in the embrasures could be observed during

follow-up. For instance, Jemt and Lekholm (2003) found a mean papilla index of

1.1 at crown placement (score 1 and 2 denote, respectively, less than half of the

height and at least half of the height of the proximal area filled by soft tissue)

while at two-year follow-up a mean score of 2.4 was found (score 3: complete

closure of proximal space with soft tissue). The majority of the papillae analyzed

were associated with papilla index scores of 2 or 3 after follow-up, but no signifi-

cant differences were observed between the different test and control groups.

With respect to the marginal peri-implant mucosal level, Schropp et al. (2005a)

reported that the clinical crown height was acceptable in significantly more cases

in the early placement group than in the conventional group at follow-up; of the

latter almost two-thirds of the crowns were assessed to be too short. The same

difference was found by Gotfredsen (2004), although not reported as significant.

Lindeboom et al. (2006) observed that gingival recession was more prominent in

the immediately-placed implant group, but the sample size was too small to dem-

onstrate a significant difference. Hall et al. (2006) found no statistical significant

differences between immediately or conventionally restored implants. Jemt and

Lekholm (2005) reported that implant crowns were on average 0.7 mm longer

than the contralateral natural crowns after five-year follow-up. The same value

was recorded by Gotfredsen (2004) after five-year and he found that 17 of the 20

implant crowns were too long. The studies by De Rouck et al. (2008) and Kan et

al. (2003) measured the levels of the midfacial gingival level before tooth removal

and after immediate implant placement and restoration. After one-year follow-up,

both studies reported a significant soft tissue loss of respectively 0.53 mm and

0.55 mm at the midfacial aspect.

Only a few studies recorded peri-implant probing pocket depths. Schropp et al.

(2005b) observed a mean reduction in probing depth of 0.5 mm during the two-

year observation period to a mean probing depth of 4.2 mm. The mean probing

depths presented by other studies were clearly lower. Studies that assessed the

presence of plaque on the surfaces of the implant restoration showed high vari-

ance in outcome from 0.5 % to 61% of sites examined. According to bleeding on

probing, the same phenomenon could be observed.

Patient satisfactionFour studies assessed patient satisfaction regarding the final aesthetics and one

study (Gotfredsen, 2004) also evaluated the general functioning of the implant

restoration. High satisfaction scores were reported. Three studies (Gotfredsen

2004, Meijndert et al. 2007, De Rouck et al. 2008) made use of a VAS (range

0-10), one study (Kan et al. 2003a) of a scale ranging from very unsatisfied (score

0) to very satisfied (score 10), and in one study (Ericsson et al. 2000) patients

were asked about their satisfaction with the aesthetic outcome.

ComplicationsThe complications described in the various articles were subdivided in biologi-

cal and technical ones. With respect to biological complications, the authors re-

ported on fistula formations, peri-implant mucositis and soft tissue dehiscences.

All fistula subsided after placement of the definitive restoration (Andersen et al.

2002, Kan et al. 2003a) or after non-invasive therapy (Gotfredsen 2004, Schropp

et al. 2005b). In the study by Schropp et al. (2005b) exposure of metal margins

was found in four patients. In three cases, the margin became exposed during

the observation period because of soft tissue recession. In one case, the metal

margin of the crown was present just after crown placement, but became covered

with peri-implant mucosa during function.

Technical complications that were notified were loosening of (temporary) abut-

ments and loosening or fractures of (temporary) crowns. In most of the cases,

abutments could be retightened and crowns could be recemented easily. In the

study by Andersen et al. (2002) three out of eight definitive crowns loosened after

approximately one year. In two of these cases, this was a direct result of a new

trauma.

It could be noticed that not all studies provided data regarding complications

other than implant loss and crestal bone resorption. Concerning the comparative

studies, only Gotfredsen (2004) found more complications in the experimen-

tal ‘early placement’ study group. However, these implants were restored with

standard abutments, while preparable abutments were used for the conventional

implants and the author believed that the technical complications were probably

more related to this difference.

dIscussIon

This systematic review assessed the outcome of single-tooth implants in terms

of implant survival, marginal bone level changes, aesthetics, soft tissue aspects,

patient satisfaction and complications. Aside from the traditional approaches of

implant installation and restoration, more progressive treatment strategies of im-

mediate or early implant placement and immediate or early loading were consid-

ered for evaluation. Unfortunately, we could not draw firm conclusions regarding

the most preferable treatment strategy, owing to the lack of controlled clinical trials.

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Notwithstanding these limitations, promising results were reported for immediate,

early and conventional single-tooth implant procedures in the aesthetic zone.

The implant survival meta-analysis on implants in the aesthetic zone up to

one year after implant restoration, revealed an overall survival rate of 95.5% (95%

CI: [93.0 – 97.1]) irrespective of the type of intervention. It should be stated that,

with respect to the loss of implants that are more than one year in function, a very

low event rate was calculated (0.007 (95% CI: [0.003 – 0.019]). In general, late

implant losses are attributed to fracture of the implant, overload and peri-implan-

titis in particular (Quirynen et al. 2007). In reference to the last, the strict in- and

exclusion criteria implemented in most of the included trials such as good oral

hygiene, uncontrolled periodontal disease or smoking concomitant with close

follow-up routines, could limit the development of peri-implantitis and thereupon

late implant failure. Of course, in this view, the relative short follow-up periods of

the included studies have to be taken into account.

The high implant survival rate (95.5% after one year) reported in the present

review, are in line with other reviews reporting on survival rates of single-tooth

implants (Creugers et al. 2000, Berglundh et al. 2002, Jung et al. 2008). However,

the last two reviews only included studies with follow-up periods of at least five

year, justifying that a comparison with our calculated survival rate should only be

made with caution. Furthermore, these reviews aggregated implant survival of

diverging indications, including anterior and posterior, and maxillary and man-

dibular single-tooth replacements. Particularly the posterior maxilla constitutes

an area of challenge due to the presence of the maxillary sinus and the low bone

density frequently found here. Long-term implant survival studies have even in-

dicated that the posterior maxilla presents the lowest survival rate (Graziani et

al. 2004). Apparently, this does not count for the survival of maxillary anterior

single-tooth implants.

The more progressive protocols, where implants are immediately installed in

fresh extraction sockets or immediately loaded, scored comparable survival per-

centages as the conventional protocol of installation and restoration. Although

no differences were noted neither in the stratified meta-analysis nor in the in-

cluded clinical trials, these results should only be conceived as a tendency, since

these were based on only a few (randomized) controlled trials and a low number

of patients.

Two studies were included investigating the most escalating approach, viz. im-

mediately loading of immediately placed implants. All implants integrated suc-

cessfully. In these case series only patients were enrolled satisfying strict inclusion

and exclusion criteria like presence of adequate bone volume without the necessity

of bone grafting, an intact labial bony plate after tooth extraction, complementary

soft tissue dimensions and ability to achieve good implant stability. It implies that

this modality should be implemented with caution and should be preceded by

careful patient selection and treatment planning. The same hold true for immedi-

ate or early implant loading of implants placed in healed sites. Studies investigat-

ing these approaches, pointed out the importance of good initial implant stability

before loading and all provisional crowns were cleared from occlusion.

It was only possible to combine the outcome measures of implant survival and

to a limited degree crestal bone changes in a stratified meta-analysis. Reasons

were that different outcomes or time points were used or some variables were

not taken into consideration. With reference to the clinical trials, for only one

outcome measure a significant difference was observed. Schropp et al. (2005a)

reported that the level of the marginal peri-implant mucosa was acceptable in

significantly more cases where implants were installed in early healed extraction

sites compared to conventionally healed sites; of the latter almost two-thirds of

the crowns were assessed to be too short. All other clinical trials failed to show

any significant differences.

Remarkably, only three studies assessed the aesthetic outcome of which only

one study made use of an objective aesthetic index. The lack of documentation of

well-defined aesthetic parameters in anterior implant research was demonstrated

earlier by Belser et al. (2004). Nowadays, two instruments are available that aim

to objectify the aesthetic outcome of single-tooth implant crowns, namely the

Implant Crown Aesthetic Index to measure the aesthetics of crown and mucosa

(Meijer et al. 2005) and the Pink Esthetic Score (Furhauser et al. 2005) which

focuses on soft tissue solely. It was concluded that both indexes showed repro-

duciblity, based on calculations of intra- and interobserver agreement. However,

the validity of these indexes was not investigated and although they show good

face validity, the construct validity in particular needs further research. Because

these indexes were developed fairly recently, this could be a prominent reason

that only Meijndert et al. (2007) used the Implant Crown Aesthetic Index, apart

from the fact that the latter authors introduced this index (Meijer et al., 2005).

Meijndert et al. (2007) reported that in 34% of the cases, the aesthetics were not

acceptable, which is a rather high percentage. It must be noted, however, that in

all cases a local bone augmentation procedure was needed prior to implantation

because of severe bone deficiencies. This implies again the significance of the

aesthetic appearance before implant treatment and that the final aesthetics might

be strongly related to that appearance. To illustrate, when the starting point is

favorable, favorable aesthetics could be expected from an implant based single-

tooth replacement, both from the patient’s and professional’s perspectives, while

an unfavorable starting point might lead to satisfactory results from the patient’s

perspective while the professionals objective judgement might be unfavorable.

This incongruity might lead easily to bias in aesthetic implant research.

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thetic outcome and patient satisfaction, more long-term research is needed, such

as cohort-studies.

In conclusion, evidence from the included literature suggest that single-tooth

implants in the aesthetic zone with natural adjacent teeth will lead to (short-term)

successful treatment outcomes regarding implant survival, marginal bone level

changes and incidence of biological and technical complications. However, with

reference to quality of study design, number of patients included and follow-up

duration, the included studies showed inadequacies. Moreover, other parameters

of utmost importance as the aesthetic outcome, soft tissue aspects, and patient

satisfaction were clearly underexposed. The question whether immediate and ear-

ly implant placement or immediate and early implant loading will result in compa-

rable – or even better – treatment outcomes than conventional implant protocols

of installation and restoration, remains inconclusive. Thus, more well-designed

(randomized) comparative trials are needed investigating objective aesthetic and

satisfaction parameters in particular, to verify these treatment strategies.

It is widely accepted that randomized controlled trials (RCTs) provide ‘gold

standard’ evidence of the effectiveness of therapies. However, there is scarcity of

existing RCTs in implant research, probably caused by medical-ethical reasons,

costs or workload involved in this type of research. Nevertheless, relevant in-

formation is not exclusively provided by RCTs for matters of longevity. Cohort-

studies, case series and clinical trials could also provide valuable longitudinal

information. Therefore, these types of studies were considered for evaluation too.

It appeared that seven eligible comparative trials could be included, of which four

studies examined immediate or early implant placement, two studies immediate

implant loading and one study focussed on different bone augmentation proce-

dures prior to implantation. Sample sizes were relatively small and presumably

underpowered to demonstrate significant differences between experimental and

conventional single-tooth implant approaches. Furthermore, not all clinical trials

randomly allocated patients to the study groups and for three trials it was unclear

if the outcome assessors were blinded. Probably, some trials were confounded

by the type of prosthetic restoration as Schropp et al. (2005b) and Gotfredsen

(2004) made use of different types of abutments and Ericsson et al. (2000) re-

ported that ceramic or metal-ceramic crowns were utilized. Probably, these vari-

ances could have their influence on parameters like the aesthetic outcome and

patient satisfaction.

The remaining studies included for this review, could be classified as case se-

ries and as a consequence were of a lower level of evidence. Although these stud-

ies were well documented and methodological acceptable within their framework,

results of these studies should be interpreted with caution. Selection and meas-

urement bias will always be present in case series, together with a potential risk

of incorporation bias, favoring the final outcome of the intervention. Moreover,

for most of the case series it was not reported or unclear whether consecutive

recruitment was used. Non-consecutive enrolment may lead to selection of pa-

tients with more favorable pre-operative conditions.

Besides the low number of RCTs and small study groups, one of the major

drawbacks of the reviewed literature was the lack of sufficient follow-up. Eight

of the included studies followed their patients for only one year. It is noteworthy

that, on the other hand, only a small number of patients were lost to follow-up. In

our opinion, the follow-up periods were too short to lead to definitive conclusions

as to whether a single-tooth implant in the aesthetic zone is a reliable therapy

over the long term. However, since there is sufficient evidence in present im-

plantology that implant losses predominately occur within the first months after

placement, the favorable short term survival rates of single implant replacements

in the anterior zone might justify the expectations of a successful long-term sur-

vival. For other parameters including aspects of the peri-implant mucosa, aes-

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supported single crown restorations. International Journal of

Oral and Maxillofacial Implants 13, 212-218.

Schneider, R. (2008) Implant replacement of the maxil-

lary central incisor utilizing a modified ceramic abutment

(Thommen SPI ART) and ceramic restoration. Journal of

Esthetic and Restorative Dentistry 20, 21-27.

Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2005a)

Interproximal papilla levels following early versus delayed

placement of single-tooth implants: a controlled clinical

trial. International Journal of Oral and Maxillofacial Implants

20, 753-761.

Schropp, L., Kostopoulos, L., Wenzel, A. & Isidor, F.

(2005b) Clinical and radiographic performance of delayed-

immediate single-tooth implant placement associated with

peri-implant bone defects. A 2-year prospective, controlled,

randomized follow-up report. Journal of Clinical Periodontol-

ogy 32, 480-487.

Tarnow, D., Elian, N., Fletcher, P., Froum, S., Magner, A.,

Cho, S.C., Salama, M., Salama, H. & Garber, D.A. (2003)

Vertical distance from the crest of bone to the height of the

interproximal papilla between adjacent implants. Journal of


Tarnow, D.P., Magner, A.W. & Fletcher, P. (1992) The effect

of the distance from the contact point to the crest of bone on

the presence or absence of the interproximal dental papilla.

Journal of Periodontology 63, 995-996.

Weber, H.P., Fiorellini, J.P. & Buser, D.A. (1997) Hard-

tissue augmentation for the placement of anterior dental

implants. Compendium Continuing Education in Dentistry 18,

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Zetu, L. & Wang, H.L. (2005) Management of inter-dental/

inter-implant papilla. Journal of Clinical Periodontology 32,

831-839.

This chapter is an edited version of the manuscript: Den Hartog, L., Meijer, H.J., Stegenga, B.,

Tymstra, N., Vissink, A., Raghoebar, G.M. Single-tooth implants with different neck designs in the

aesthetic zone: a randomized clinical trial. Clinical Oral Implants Research (accepted for publica-

tion, 2010)

3.

Single-tooth implants with different neck designs in

the aesthetic zone: a randomized clinical trial

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AbstrAct

Aim: To compare single-tooth implants in the aesthetic zone with different

neck designs for marginal bone level changes and clinical outcome meas-

ures.

Material and Methods: 93 patients with a missing anterior tooth in the

maxilla were randomly assigned to be treated with an implant with a 1.5

mm smooth neck (‘smooth group’), a moderately rough neck with grooves

(‘rough group’) or a scalloped moderately rough neck with grooves (‘scal-

loped group’). Implants were installed in healed sites and were loaded after

3 months. Follow-up visits were conducted at 6 and 18 months after im-

plant placement.

Results: The scalloped group showed significantly more radiographic bone

loss from implant placement to 18 months (2.01 ± 0.77 mm) compared to

the smooth group (1.19 ± 0.82 mm) and rough group (0.90 ± 0.57 mm).

Furthermore, the scalloped group showed significantly deeper probing

pocket depths and a significantly higher bleeding score. There were no

between-group differences in soft tissue levels. Survival rates were 97% for

the smooth group and 100% for the rough and scalloped groups (P>0.05).

No significant differences in outcome measures were found between the

smooth group and rough group.

Conclusion: For anterior tooth replacements, implants with a scalloped neck

show more marginal bone loss and less favorable clinical outcome com-

pared to implants with a 1.5 mm smooth neck or implants with a rough

neck.

IntroductIon

A lost or congenitally missing tooth in the anterior region usually requires pros-

thetic replacement for functional and aesthetic reasons. The aesthetic outcome

is determined by the appearance of the crown and the surrounding soft tissue,

which should be harmonious with the adjacent dentition.

Currently, dental implants are widely used for dental rehabilitation, even in

aesthetically delicate areas as the anterior maxilla. The level of the peri-implant

marginal bone is related to the level of the peri-implant mucosa (Bengazi et al.

1996; Hermann et al. 1997, 2000, 2001; Chang et al. 1999) which, in turn, is com-

monly considered a major factor determining the aesthetic outcome (Furhauser

et al. 2005; Meijer et al. 2005). Loss of peri-implant marginal bone could therefore

affect the level of the peri-implant mucosa and hence the final aesthetic outcome.

Furthermore, marginal bone loss may induce pocket formation, which could be

unfavorable for long-term health of the peri-implant tissue (Rams et al. 1984;

Heydenrijk et al. 2002).

There is evidence that the design of the implant neck influences the amount

of marginal peri-implant bone loss (Shin et al. 2006; Lee et al. 2007; McAllister

2007; Bratu et al. 2009; Nickenig et al. 2009). Although the traditional smooth

implant neck is accompanied by the least accumulation of plaque (Teughels et

al. 2006; Baldi et al. 2009), several studies have shown more marginal bone loss

around these implants compared to implants with a rough surface topography at

the implant neck (Shin et al. 2006; Bratu et al. 2009; Nickenig et al. 2009). Fur-(Shin et al. 2006; Bratu et al. 2009; Nickenig et al. 2009). Fur-Fur-

thermore, it has been reported that retention elements at the implant neck, such

as grooves or microthreads, favor the preservation of marginal bone (Palmer et al.

2000; Shin et al. 2006; Lee et al. 2007). In addition, it has been suggested that an

implant neck with a scalloped implant platform might preserve proximal marginal

bone (Wohrle 2003; Kan et al. 2007; McAllister 2007). Such a scalloped implant

neck would mirror the natural alveolar ridge curvature, particularly in the anterior

zone, and consequently a more non-violent position of the implant-abutment in-

terface could be realized compared to common flat platform implant designs.

There is, however, a paucity of well-designed trials addressing the influence

of the implant neck design on bone and soft tissue parameters in single implant

cases in the aesthetic zone (Den Hartog et al. 2008). Therefore, the main objec-

tive of our study was to compare the marginal bone level change around single-

tooth implants in the maxillary aesthetic zone with a 1.5 mm smooth neck, a

moderately rough neck with grooves and a scalloped moderately rough neck with

grooves. In addition, the influence of the implant neck architecture on soft tissue

levels and clinical outcome variables was taken into consideration.

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PatientsPatients referred to the department of Oral and Maxillofacial Surgery (University

Medical Center Groningen, University of Groningen, Groningen, the Netherlands)

for single implant treatment in the maxillary anterior region were considered for

inclusion if they fulfilled the following criteria:

at least 18 years of age;-

one missing tooth being an incisor, canine or first premolar in the maxilla -

with adjacent natural teeth;

adequate oral hygiene, i.e. modified plaque index score (Mombelli et al. 1987) -

and modified sulcus bleeding index score ≤ 1 (Mombelli et al. 1987);

mesial-distal width of diastema at least 6 mm. -

Exclusion criteria were:ASA score ≥ III (Smeets et al. 1998);-

presence of clinically active periodontal disease as expressed by probing -

pocket depths ≥ 4 mm and bleeding on probing (index score > 1);

presence of peri-apical lesions or any other abnormalities in the anterior re-resence of peri-apical lesions or any other abnormalities in the anterior re--

gion as detected on a radiograph;

smoking; -

a history of radiotherapy to the head and neck region. -

Study designThis prospective, randomized clinical trial was approved by the Medical Ethical

Committee of the University Medical Center Groningen. Patients were included

between January 2005 and February 2008. A written informed consent was ob-

tained from all eligible patients before enrolment.

A specifically designed locked computer software program was used to ran-

domly assign patients to one of three study groups to be treated with:

a 1.5 mm smooth (‘machined’) implant neck (Replace Select Tapered, Nobel -

Biocare AB, Göteborg, Sweden) – ‘smooth’ group (Figure 1a);

a moderately rough implant neck with grooves (NobelReplace Tapered -

Groovy, Nobel Biocare AB) – ‘rough’ group (Figure 1b);

a scalloped moderately rough implant neck with grooves (NobelPerfect -

Groovy, Nobel Biocare AB) – ‘scalloped’ group (Figure 1c).

Randomization by minimization (Altman 1991) was used to balance possible

prognostic variables between the three treatment groups. Minimization was used

for the variables age (≤30 years, >31 ≤ 60 years, > 60 years), location of the im-

plant site (central or lateral incisor, canine or first premolar) and whether or not a

pre-implant augmentation procedure was indicated based on a clinical and diag-

nostic cast assessment. The allocation result was kept in a locked computer file

that was not accessible for the examiner and the practitioners. The surgeon that

inserted the implants was informed about the allocation on the day of surgery.

Intervention procedureAll implants were placed in healed sites. A minimal period of three months af-

ter tooth removal was adopted allowing the extraction site to heal. When bone

volume was insufficient for implant placement, a bone augmentation procedure

was carried out. As a grafting material, autogenous bone was used together with

anorganic bovine bone (Geistlich Bio-Oss®, Geistlich Pharma AG, Wolhusen,

Switzerland) covered with a Geistlich Bio-Gide® membrane (Geistlich Pharma

AG). Implants were inserted three months after the augmentation procedure.

One day prior to implant surgery, patients started taking antibiotics (amoxicil-

lin 500 mg, 3 times daily for 7 days or clindamycin 300 mg, 4 times daily for 7

days in case of amoxicillin allergy) and using a 0.2% chlorhexidine mouthwash

(2 times daily for seven days) for oral disinfection. Following local anaesthesia, a

slightly palatal crest-incision was made with extensions through the buccal and

palatal sulcus of the adjacent teeth and a divergent relieving incision at the distal

tooth. A minimal mucoperiosteal flap was prepared to expose the alveolar ridge.

The implant site was prepared by using a surgical template that was fabricated in

the dental laboratory, based on the prospective implant crown in its ideal position.

All implants were installed with a torque controller (OsseoCare, Nobel Biocare

AB) adjusted to an insertion torque of 45 Ncm and by using a manual torque

wrench (Nobel Biocare AB) for fine-tuning of the implant depth. The shoulder

of the implant was placed at a depth of 3 mm apical to the most facial and cervi-

cal aspect of the prospective clinical crown for proper emergence profile. For the

scalloped implants the mid-facial part of the implant shoulder was taken as a re-

ference. In all cases the alveolar bone was levelled to the implant shoulder. When

part of the implant remained uncovered or when the bone wall thickness facially

to the implant was < 2mm, a local augmentation procedure was performed with

autogenous bone chips collected during implant bed preparation and anorganic

bovine bone (Geistlich Bio-Oss®) covered with a Geistlich Bio-Gide® membrane.

The wound was closed with Ethilon 5-0 nylon sutures (Johnson & Johnson Gate-

way, Piscatatway, United States). During the healing phase, patients were wearing

a removable partial denture that did not interfere with the wound. After three

months, implants were uncovered and a healing abutment (Nobel Biocare AB)

was installed.

One week after the second stage operation, an implant-level impression was

made. In the dental laboratory, a screw-retained provisional crown was fabricated

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and at T6m

and T18m

, together with digital photographs of the implant and con-

tralateral tooth at T18m

taken with the same camera. For calibration of the photo-

graphs, a calibrated probe was held in close contact and parallel to the long axis

of a tooth adjacent to the implant. By using the same device, both the radiographs

and the photographs were taken from the same horizontal and vertical angula-

tion. All measurements were performed by one examiner and were blinded for

the photographs. The radiographic examination could not be blinded, since the

type of implant neck could be derived directly from the radiographs. Full-screen

analysis of the radiographs was performed using specifically designed software.

First, the radiographs were calibrated according to the known diameter of the

implant. Next, different reference points were marked and marginal bone levels

proximal to the implant were measured according to the first bone-to-implant

contact together with marginal bone levels of the adjacent teeth (Figures 1a,b,c).

Full-screen analysis of the photographs was performed using Adobe Photoshop

(Adobe Photoshop CS3 Extended, Adobe Systems Inc., San Jose, USA). After ca-

libration, mid-facial mucosal and papilla levels of the implant were measured

after definitive crown placement (at T6m

and T18m

). Mid-facial gingival levels of the

adjacent teeth were measured from Tpre

. The incisal edges of the implant crown

and adjacent teeth were used as reference.

To assess the reliability of the radiographic and photographic examinations,

14 radiographs and 14 photographs from each study group (i.e., 15% of all radi-

ographs and photographs) were randomly selected and were measured by two

examiners and by one examiner twice with a two-week interval. The intra-observer

agreement of the photographic examination was tested earlier and reported as

good with a mean difference of 0.11±0.02 mm between both times of measure-

ments (Meijndert et al. 2004). The facial peri-implant mucosal level (PML) was

compared with the gingival level of the contralateral tooth on photographs taken

at T18m

and was judged as follows: identical level; slight deviation <1.5 mm; major

deviation ≥ 1.5 mm. An acceptable reliability of this method was reported in ear-

lier studies (Gehrke et al. 2008).

Clinical assessmentsBefore implant placement (T

pre), and 6 (T

6m) and 18 months after implant pla-

cement (T18m

), patients were seen for clinical data collection. Both the implant

and the adjacent teeth were analyzed at the facial aspect. All data were retrieved

by one examiner according to a specified protocol. The following variables were

evaluated:

plaque- , using the modified plaque index (Mombelli et al. 1987): 0 = no detec-

tion of plaque, 1 = plaque can be detected by running a probe across the sur-

face of the crown, 2 = plaque visible with the naked eye, and 3 = abundance

by means of an engaging temporary abutment and composite (Solidex, Shofu

inc., Kyoto, Japan). The provisional crowns were screwed directly onto the implant

with 32 Ncm as indicated by a manual torque wrench (Nobel Biocare AB). After

a provisional phase of three months (i.e., six months post-implant placement), a

final impression was taken on implant level. In the laboratory, a waxing of the defi-

nitive crown was made that was cut back to the desired form of the abutment. The

wax-up was scanned to retrieve individualized zirconia abutments (Procera, Nobel

Biocare AB) for the implants in the smooth group and rough group and individua-

lized titanium abutments (Procera, Nobel Biocare AB) for the implants in the scal-

loped group, since zirconia abutments were not available for these implants. A

zirconica Procera coping (Procera, Nobel Biocare AB) was luted over the titanium

abutments in order to create an abutment with a zirconia outside. Depending on

the location of the screw access hole, the final crown was either cement-retained

using a zirconia coping (Procera, Nobel Biocare AB) or screw-retained by fusing

porcelain directly to the abutment. Abutment screws were torqued with 32 Ncm.

Cement-retained crowns were cemented with glass ionomer cement (Fuji Plus,

GC Europe, Leuven, Belgium). For more details regarding product specifications,

we refer to a previous clinical report (Den Hartog et al. 2009).

All surgical procedures were performed by a single experienced oral and maxil-

lofacial surgeon. The prosthetic procedure was accomplished by two experienced

prosthodontists and all crowns were fabricated by one dental technician.

Outcome measuresThe primary outcome measure of this study was marginal bone level change proxi-

mal to the implant 18 months after implant placement measured on radiographs.

Secondary outcome measures were implant survival, change in peri-implant

mucosal level and its position compared with the gingival level of the contral-

ateral tooth, papilla volume (papilla index), amount of plaque (plaque index),

bleeding after probing (bleeding index) and probing pocket depth. In addition

to the implant, also the adjacent teeth were analyzed. The operationalization of

variables is described below.

Radiographic and photographic assessmentsAfter implant placement (baseline, T

0) and after 6 (T

6m, after definitive crown

placement, equals 3 months of functional loading) and 18 months (T18m,

equals 12

months after definitive crown placement and 15 months of functional loading),

standardized digital intra-oral radiographs were taken according to a long-cone

paralleling technique and with a device as described by Meijndert and colleagues

(Meijndert et al. 2004). The same device was used to gather standardized digital

photographs (camera: Fuji-film FinePix S3 Pro) before implant placement (Tpre

)

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of plaque;

bleeding- , using the modified sulcus bleeding index (Mombelli et al. 1987): 0 =

no bleeding running a periodontal probe along the sulcus, 1 = isolated bleed-

ing spots visible, 2 = a confluent red line of blood along the gingival margin,

3 = profuse bleeding;

volume of the interproximal papilla- , using the papilla index (Jemt 1997): 0 = no

papilla, 1 = less than half of the papilla fills up the proximal space; 2 = at least

half of the papilla is present but not all the way up to the contact point; 3 =

papilla fills up the entire proximal space; 4 = papilla is hyperplasic;

probing pocket depth,- measured to the nearest 1 mm using a manual peri-

odontal probe (Williams Color-Coded Probe, Hu-Friedy, Chicago, USA) at the

mesio-facial, mid-facial and disto-facial aspects of the implant crown and

adjacent teeth.

During follow-up, implant survival was registered (defined as the existence of

an implant in the oral cavity (Laney 2007)) and complications were registered.

Data analysisSample size was calculated using G*power version 3.1 (Faul et al. 2009). We

considered 0.5 mm of radiographic marginal bone loss from implant placement

to 18 months thereafter, as a relevant difference between study groups. With an

expected standard deviation of 0.6 mm as derived from literature (Den Hartog et

al. 2008), a two-sided significance level of 5% and a power of 90%, a minimum of

81 patients would be required (i.e., 27 per group). To deal with a withdrawal, the

minimum number of patients per group was set at 31.

The intra- and interobserver agreement for the radiographic and photographic

assessments were expressed as the 95% limits of agreement (Altman 1991), re-

presenting the interval containing 95% of the differences between the observations

to be compared. In addition, intraclass correlation coefficients were calculated.

For between-group comparisons of numeric and normally distributed vari-

ables (assessed using Kolmogorov-Smirnov test), one-way analyses of variance

were conducted, followed by post-hoc multiple comparison tests (Tukey’s test) in

case of statistical significance. For pairwise within-group comparisons, t tests for

matched samples were used. Variables that were not normally distributed were

statistically explored with Kruskal-Wallis tests for between-group comparisons,

followed by post-hoc Mann-Whitney tests to compare two independent condi-

tions. Friedman tests and Wilcoxon signed-rank tests were applied for more-

than-two within-group comparisons and to compare two dependent conditions,

respectively. Categorical variables were statistically explored using Chi-square or

Fisher exact tests.

A multivariate linear regression analysis was performed to identify potential

Figure 1a. Schematic drawing of the radiographic evaluation of 1.5 mm smooth implant neck (Replace Select Tapered, Nobel Biocare AB).

Figure 1c. Schematic drawing of the radiographic evaluation of scalloped moderately rough im-plant neck with grooves (Nobel-Perfect Groovy, Nobel Biocare AB).

Abbreviations: ref = reference line, A and B = distances from reference line to marginal bone levels of implant and adjacent teeth.

Figure 1b. Schematic drawing of the radiographic evaluation of moderately rough implant neck with grooves (NobelReplace Groovy, Nobel Biocare AB).

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predictive factors for the primary outcome of change in marginal bone level from

baseline (T0) to T

18m. The following predictors were entered using a block wise

entry procedure: type of implant, augmentation before implant surgery, implant-

tooth distance, implant site (I1/I2/C/P1), type of definitive implant crown (screw-

or cement-retained), age and gender. Pearson’s and Spearman’s correlations

were used to explore possible significant relationships between marginal bone

level change from T0 to T

18m and the secondary outcome measures.

In all analyses, a significant level of 0.05 was chosen. Data were analysed using

the Statistical Package for Social Sciences (version 16.0, SPSS Inc, Chicago, USA).

results

PatientsA total of 93 patients was allocated to the study groups of this trial (Table 1). Most

of the teeth that were lost had a history of trauma. All implants could be inserted

with good primary stability (> 45Ncm). Details about the surgical and prosthetic

procedures applied in the various treatment groups are depicted in table 1. In two

patients (one in the smooth group and one in the scalloped group) a pre-implant

augmentation procedure, which was not indicated beforehand appeared to be

necessary during implant surgery and the implants were inserted three months

later. All patients attended the follow-up visits at T18m

. One patient in the scallo-

ped group did not attend the recall visit at T6m

.

Reliability of radiographic and photographic assessmentsThe assessment of the intra-observer agreement of the radiographic examination,

revealed a mean difference between the repeated measurements of -0.01 ± 0.25

mm (limits of agreement: - 0.50 mm and 0.50 mm). A difference in the range of

-0.2 to 0.2 mm was found in 70.7% of the measurements and a difference in the

range of -0.5 to 0.5 mm in 92.8% of the measurements (we considered 0.5 mm as

a relevant difference in our power analysis). The assessments of the radiographic

and photographic inter-observer agreement, showed mean differences between

the observers of 0.08 ± 0.31 mm for the radiographs (limits of agreement: -0.69

and 0.54 mm) and -0.02 ± 0.18 mm for the photographs (limits of agreement:

-0.38 and 0.34 mm). For the radiographs, an inter-observer difference in the range

of -0.2 to 0.2 mm and in the range of -0.5 to 0.5 mm was found in 54.2% and

89.5 % of the measurements respectively. For the photographs, these percent-

ages were 83.5% and 96.1%.

The intraclass correlation coefficients were 0.96 and 0.99 for the radiographic

inter- and intra-observer agreement, respectively, and 0.99 for the photographic

inter-observer agreement, all signifying high levels of agreement.

Change in marginal bone levelThe total amount of mean marginal bone loss (mesial and distal implant sides

combined) between baseline (T0, implant placement) and T

18m (18 months after

implant placement) was 1.19 ± 0.82 mm in the smooth group [95% confidence in-

terval (CI): 0.89-1.49], 0.90 ± 0.57 mm in the rough group [95% CI: 0.70-1.10] and

2.01 ± 0.77 mm in the scalloped group [95% CI: 1.74-2.28] and was significantly

different (Figure 2). The scalloped group showed significantly more marginal bone

loss from T0 to T

18m at both proximal implant sides compared to the other study

groups (Table 2). There were no significant differences between the smooth and

rough study groups. The most extensive marginal bone loss was observed dur-

ing the first evaluation period (from T0 to T

6m, mesial and distal sides combined:

smooth group 1.05 ± 0.69, rough group 0.80 ± 0.57, scalloped group 1.77 ± 0.82)

and was significantly lower for the second evaluation period (from T6m

to T18m

:

Table 1. Baseline characteristics and treatment specifications per study group.

VariableSmooth group(n=31)

Rough group(n=31)

Scalloped group(n=31)

Mean age ± standard devia-tion (range)

37.2 ± 12.9 (18-60) 40.1 ± 14.4 (18-67) 40.1 ± 17.2 (19-80)

Male/female ratio 15/16 17/14 14/17

Implant site location I

1 / I

2 / C / P

120 / 7 / 1 / 3 18 / 8 / 3 / 2 18 / 6 / 3 / 4

Cause of tooth absence Fracture (crown or root) Agenesis Endodontic failure Periodontal failure Root resorption

193216

154822

213223

Augmentation before im-plant surgery*

12 11 10

Implant-tooth distance (mm) Mean ± SD Range

2.36 ± 0.760.70 – 4.59

2.17 ± 0.770.45 - 5.26

2.30 ± 0.650.56 ± 5.15

Type of final restoration Screw-retained Cement-retained

1514

1219

1120

*implant was placed 3 months later

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52 53

smooth group 0.13 ± 0.31, rough group 0.11 ± 0.28, scalloped group 0.23 ± 0.43).

Marginal bone loss at the adjacent teeth was limited, and there were no signifi-

cant differences between the study groups.

Figure 2. Error plot of marginal bone loss from implant placement to 18 months thereafter.

Clinical outcomesOne implant in the smooth group was lost five months after implant placement

during the provisional phase. It appeared that this implant was not integrated.

The implant survival rate at T18m

was 96.8 % for the smooth group and 100% for

the rough and scalloped study groups.

The photographic assessments did not yield between-group differences in mid-

facial peri-implant mucosal levels and papilla levels during follow-up (Table 2).

After definitive crown placement, the level of the mid-facial peri-implant mucosa

remained stable, while a gain in papilla height was observed (Table 2). The mid-

facial gingival level of the adjacent teeth showed a mean recession of 0.18±0.45

mm, 0.28±0.36 mm and 0.25±0.29 mm in the smooth, rough and scalloped

groups, respectively. It appeared that the level of the peri-implant mucosa (PML)

was identical to the contralateral tooth in 14 cases (48%) in the smooth group, 13

(42%) in the rough group, and 18 (58%) in the scalloped group. A major discrep-

ancy (≥ 1.5 mm) was found in 4 cases (14%) in the smooth group, 4 in the rough

group (13%) and 2 in the scalloped group (6%). Differences were not significant.

Tab

le 2

. C

han

ges

in

mar

gin

al b

on

e le

vel

and

mar

gin

al s

oft

tis

sue

leve

l an

d p

robi

ng

po

cket

dep

ths

at i

mpl

ant

and

to

oth

sid

es f

rom

ba

seli

ne

to 1

8 m

on

ths.

Var

iabl

eB

asel

ine# -

T6

mT

6m

- T18

mB

asel

ine# -

T18

m

Smoo

th(n

=30

)†

Rou

gh(n

=31)

Scal

lope

d(n

=31)

Smoo

th(n

=30

)†

Rou

gh(n

=31)

Scal

lope

d(n

=30

)‡

Smoo

th(n

=30

)†

Rou

gh(n

=31)

Scal

lope

d(n

=31)

Mar

gin

al b

one

leve

lch

ange

s (m

m)

M

esia

l of

impl

ant

-0.9

6 ±

0.7

6-0

.79

± 0

.62

-1.8

4 ±

0.9

3*-0

.13

± 0

.45

-0.1

3 ±

0.4

0-0

.16

± 0

.58

-1.1

0 ±

0.8

3-0

.91

± 0

.66

-2.0

1 ±

0.7

4*

D

ista

l of

impl

ant

-1.1

5 ±

0.8

2-0

.81

± 0

.76

-1.7

0 ±

0.9

8*-0

.13

± 0

.47

-0.0

9 ±

0.4

1-0

.30

± 0

.46

-1.2

7 ±

1.0

9-0

.90

± 0

.77

-2.0

0 ±

1.0

1*

M

esia

l too

th s

ide

-0.2

3 ±

0.4

5-0

.25

± 0

.38

-0.3

0 ±

0.5

0-0

.01

± 0

.25

0.0

3 ±

0.2

80

.02

± 0

.25

-0.2

4 ±

0.5

0-0

.17

± 0

.40

-0.2

8 ±

0.5

0

D

ista

l too

th s

ide

-0.2

0 ±

0.4

2-0

.18

± 0

.34

-0.2

9 ±

0.4

40

.02

± 0

.28

-0.0

3 ±

0.4

20

.02

± 0

.24

-0.1

7 ±

0.4

4-0

.29

± 0

.50

-0.2

7 ±

0.5

4

Impl

ant b

one

loss

(%)§

≤

1 m

m47

.96

2.9

18.0

*9

6.1

100

94.

241

.356

.512

.3*

1

-2 m

m37

.533

.938

.03.

90

5.8

47.8

38.7

35.1

≥

2 m

m14

.63.

244

.00

00

10.9

4.8

52.6

Mar

gin

al s

oft t

issu

e le

vel c

han

ges

(mm

)

M

esia

l im

plan

t pap

illa

0.1

2 ±

0.4

40

.19

± 0

.29

0.2

7 ±

0.4

7

D

ista

l im

plan

t pap

illa

0.1

4 ±

0.3

50

.35

± 0

.52

0.2

4 ±

0.4

3

M

id-f

acia

l of

impl

ant

-0.0

9 ±

0.2

3-0

.09

± 0

.34

0.0

3 ±

0.2

2

M

esia

l too

th-0

.14

± 0

.31

-0.1

3 ±

0.3

8-0

.19

± 0

.23

-0.1

0 ±

0.2

6-0

.09

± 0

.25

-0.0

2 ±

0.2

5-0

.24

± 0

.50

-0.2

2 ±

0.3

6-0

.21

± 0

.36

D

ista

l too

th-0

.14

± 0

.39

-0.3

3 ±

0.5

1-0

.37

± 0

.53

0.0

2 ±

0.2

30

.00

± 0

.30

0.1

0 ±

0.2

1-0

.12

± 0

.44

-0.3

3 ±

0.3

6-0

.28

± 0

.44

3

Impl

ant n

eck

desi

gns

54 55Tab

le 2

. (c

on

tin

ued

)

Bas

elin

e#T

6m

T18

m

Smoo

thR

ough

Scal

lope

dSm

ooth

R

ough

Scal

lope

dSm

ooth

R

ough

Scal

lope

d

Poc

ket d

epth

(mm

)

M

esia

l of

impl

ant

3.45

± 0

.87

3.0

3 ±

0.8

93.

80 ±

1.2

4*3.

34 ±

1.2

03.

19 ±

0.9

14.

42 ±

1.1

8*

D

ista

l of

impl

ant

3.41

± 1

.05

3.50

± 0

.82

3.6

7 ±

0.9

93.

24 ±

0.7

93.

81 ±

1.2

84.

63

± 1.

13*

M

id-f

acia

l of

impl

ant

3.34

± 0

.72

3.0

7 ±

0.7

43.

47 ±

0.9

73.

10 ±

0.8

23.

32 ±

0.7

93.

65

± 0

.92*

P

roxi

mal

of

teet

h§

2.20

± 0

.57

2.0

3 ±

0.5

12.

11 ±

0.5

02.

18 ±

0.3

71.

92

± 0

.49

1.9

2 ±

0.3

92.

15 ±

0.4

11.

99

± 0

.60

1.9

9 ±

0.6

5

M

id-f

acia

l of

teet

h1.

27 ±

0.3

91.

37 ±

0.3

91.

45 ±

0.4

41.

29 ±

0.3

91.

40 ±

0.5

31.

28 ±

0.3

71.

24 ±

0.3

21.

37 ±

0.3

41.

37 ±

0.3

9

Plu

s-m

inu

s va

lues

are

mea

ns

± st

anda

rd d

evia

tion

s.

#Aft

er im

plan

t pla

cem

ent f

or b

one

leve

ls, b

efor

e im

plan

t pla

cem

ent f

or s

oft t

issu

e le

vels

an

d pr

obin

g po

cket

dep

ths.

† O

ne

impl

ant w

as lo

st.

‡ O

ne

pati

ent d

id n

ot a

tten

d fo

llow

-up

visi

t T6

m.

* P

< 0

.05,

bet

wee

n-g

rou

p co

mpa

riso

n.

§ M

esia

l an

d di

stal

sid

es c

ombi

ned

.

Abb

revi

atio

ns:

T6

m =

6 m

onth

s po

st-im

plan

t pla

cem

ent,

T18

m =

18

mon

ths

post

-impl

ant p

lace

men

t.

Between-group analyses showed significant differences for probing pocket

depths at T18m

at all sides and mesially at T6m

(Table 2). Post-hoc analyses revealed

significantly deeper probing pocket depths in the scalloped group at T18m

com-

pared to the smooth group at all sides and compared to the rough group at both

proximal sides. At T6m

at mesial sides, significantly deeper probing pocket depths

were found in the scalloped group compared to the rough group.

Bleeding index scores were significantly higher for the scalloped group at T18m

(Figure 3). There were no between-group differences in plaque scores and papilla

index scores (Figure 4) at both follow-up examinations and no differences in

bleeding scores at T6m.

Plaque index scores were low at both follow-up visits. At

T18m

, a plaque score of 1 was assigned to one implant in the smooth group and 3

implants in the other study groups. All other implants did not show any plaque.

With regard to between-group comparisons of the adjacent teeth, no differences

in clinical outcomes were found. Bleeding index scores of the adjacent teeth were

significantly lower compared to the scores of the implants.

Figure 3. Frequency distribution of bleeding index scores of implants and adjacent teeth at 18 months after implant placement.

Cha

pter

3 3

Impl

ant n

eck

desi

gns

56 57

Within-group analyses showed that the volume of the papillae, expressed in

papilla index scores, increased significantly during follow-up (smooth implants,

both papillae; rough implants, distal papillae; scalloped implants, distal papillae)

(Figure 4). The scalloped implants showed significantly higher bleeding index

scores at T18m

compared to T6m

. The adjacent teeth showed significantly higher

plaque scores at Tpre

versus T6m

and T18m.

Complications that arose during the restorative phase and after placement

of the definitive crown are depicted in Table 3. The scalloped implants showed

the most complications. All complications could be successfully resolved. The

complications of biological origin were treated with a minimally invasive surgical

approach. For the patient that developed peri-implantitis (symptoms: implant

probing depth 6 mm with profuse bleeding, progressive radiographic bone loss,

pain) cement-remnants together with a moderate oral hygiene and recommenced

smoking, probably were the etiologic factors. During treatment of one fistula,

cement remnants were removed, while the etiology of the other fistula was un-

clear.

Table 3. Complications during 18 months of follow-up.

ComplicationSmooth group

(n=30)†

Rough group (n=31)

Scalloped group (n=31)

Mobile provisional crown 2 1 2

Fracture of provisional crown

0 1 1

Mobile definitive crown 0 0 3

Porcelain fracture 0 26 (2 in one

patient)

Bent fixation screw (after trauma)

1 0 0

Peri-implantitis 0 1 0

Fistula 0 0 2

† One implant was lost.

Regression and correlation analysisThe regression analysis revealed that only the type of implant neck was signifi-

cantly associated with the change in marginal bone level (Table 4). The other

independent variables did not contribute significantly. The implant site could not

be included in the analysis, since there were not enough cases in which a tooth

other than a central incisor was replaced. The correlation analysis showed that

the amount of marginal bone loss at both proximal sides was positively related to

probing pocket depth at that side (correlation coefficient mesial side 0.27; distal

side 0.32). Furthermore, the total amount of marginal bone loss (mesial and dis-

tal sides combined) was positively correlated to probing pocket depth mid-facially

with a coefficient of 0.34. No other significant correlations were found.

Figure 4. Frequency distribution of papilla index scores at 6 and 18 months after implant placement.

Cha

pter

3 3

Impl

ant n

eck

desi

gns

5958

Although not supported by our data, several other studies have demonstrated

significantly more marginal bone loss around implants with a smooth neck com-

pared to a rough neck (Hermann et al. 2000; Shin et al. 2006; Schwarz et al. 2008;

Bratu et al. 2009; Nickenig et al. 2009; Stein et al. 2009). Also, it has been re-Also, it has been re-

ported that retention elements, such as microthreads or grooves, could decrease

marginal bone resorption (Shin et al. 2006; Lee et al. 2007; Nickenig et al. 2009).

Since these studies mainly focused on posterior tooth replacements or were non-

clinical of origin, it is questionable whether these results can be extrapolated to

our findings. For instance, Nickenig et al. (2009) compared smooth and rough

implants for restoring missing mandibular molars. They reported that from im-

plant placement to two years thereafter, the rough implant neck with grooves was

superior to the smooth neck in reducing radiographic marginal bone loss (mean

bone loss 0.5 mm vs 1.1 mm, standard deviation not reported, however). We

found 0.90 ± 0.57 mm marginal bone loss around the moderately rough implant

neck and 1.19 mm ± 0.82 mm around the smooth implant neck.

In our study, all implants were placed at a 3 mm depth from the implant shoul-

der to the buccal and cervical aspect of the prospective clinical crown. All im-

plants were levelled with the alveolar bone crest so that the whole implant neck

was covered with bone (in some cases, an additional augmentation procedure

was performed to cover the implant neck). It has been found that the position of

the implant-abutment interface relative to the bone crest at the time of implant

placement is a significant factor for marginal bone loss (Hermann et al. 2000;

Broggini et al. 2006; Jung et al. 2008). An inflammatory reaction at the implant-

abutment interface due to microbial leakage seems to be a major factor for this

bone loss. A more apical position of the implant-abutment interface will increase

the inflammatory reaction and will induce more marginal bone loss. Since in our

study the implant-abutment interface was closely related to the bone crest, possi-

bly surface roughness or grooves could not realize less marginal bone resorption

than a smooth surface.

We found significantly more marginal bone loss around the scalloped implant

neck compared to the other implants with common flat platforms. To date, only

case reports and cases series have been published addressing the outcome of

scalloped implants (Mitrani et al. 2005; Nowzari et al. 2006; Kan et al. 2007;

McAllister 2007; Noelken et al. 2007). Unfortunately, no other clinical trials on

the scalloped implant have been published. Since case series are highly suscep-. Since case series are highly suscep-Since case series are highly suscep-

tible to bias, results of these studies should be interpreted with caution. When

placed in healed extraction sites, the mean radiographic bone loss ranged from

1.5 to 2.1 mm (standard deviations around 1 mm) between implant placement

and 12 months thereafter (Nowzari et al. 2006; Kan et al. 2007; McAllister 2007).

These values were found for the original version of the scalloped implant with a

DiscussionThis study compared the effect of three different implant neck designs on preser-

vation of marginal bone for single-tooth implants in the maxillary aesthetic zone.

Implants had a 1.5 mm smooth implant neck (‘smooth group’), a moderately

rough implant neck with grooves (‘rough group’) and a scalloped moderately

rough implant neck with grooves (‘scalloped group’). The results of our study

showed that after 18 months of follow-up, there was a significant difference in

radiographic marginal bone loss between the study groups that could entirely be

attributed to the scalloped group. In addition to more bone loss, the scalloped

group revealed deeper probing pocket depths and higher bleeding scores than

the smooth group and rough group. Post-hoc analyses did not reveal significant

differences in outcome between the smooth group and rough group. The smooth

and rough group revealed favorable treatment outcomes in terms of bone loss,

implant survival, complications and soft tissue aspects, which are in line with

values reported in other studies on single-tooth implants placed in the anterior

maxilla (Den Hartog et al. 2008).

Table 4. Outcome of multiple regression analysis.

B SE B ß

Step 1

Constant 2.01 0.13

Type of implant Scalloped vs. Rough Scalloped vs. Smooth

-1.12-0.83

0.180.18

-0.62*-0.46*

Step 2

Constant 1.93 0.52

Type of implant Scalloped vs. Rough Scalloped vs. Smooth

-1.07-0.94

0.180.18

-0.61*-0.52*

Augmentation before implant surgery

-0.02 0.16 -0.02

Implant-tooth distance 0.20 0.11 0.17

Type of definitive crown -0.15 0.15 -0.09

Age -0.01 0.01 -0.14

Gender 0.12 0.15 0.07

R2 = 0.33 for Step 1; Δ R2 = 0.06 for Step 2 (P>0.05).

* P < 0.05

Abbreviations: SE = Standard Error.

Cha

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3 3

Impl

ant n

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60 61

observed in the other study groups. With respect to the volume of the papilla, it

should be realized that the bone level at the adjacent teeth may play a significant

role. It is known that the level of the papilla is highly related to the bone level next

to the adjacent teeth (Choquet et al. 2001; Kan et al. 2003; Romeo et al. 2008).

We observed only minor marginal bone loss at the adjacent teeth without differ-

ences between study groups. This prominent role of the adjacent teeth may also

apply to the preservation of the PML. Besides, for this variable, the soft tissue

level before implant placement could be more relevant to the future PML while

the future PML is to a lesser degree related to the amount of marginal bone loss

around the implant neck. All implants were placed in healed extraction sites, one

third of which were augmented. This might have had a significant effect on the

level of the PML before implant placement.

We measured deeper pocket depths around the scalloped implants together

with higher bleeding scores at T18m

compared to the other study groups. These

values increased significantly within the scalloped group during follow-up, despite

radiographic marginal bone levels remaining stable. It seems that the peri-implant

tissue in the scalloped group developed more marginal inflammation with time as

confirmed by the higher bleeding scores. However, the few studies on single-tooth

implants in the anterior maxillary region that have considered pocket depths, re-

ported comparable pocket depths as we observed around the scalloped implants

(Den Hartog et al. 2008). Although there is no evidence that pocket depth is a risk

factor for developing peri-implantitis and deteriorates the prognosis (Schropp et

al. 2005b; Heitz-Mayfield 2008), we believe that pocket depths should be limited

and remain stable over time to facilitate healthy peri-implant tissue.

From this study, it can be concluded that there are differences between anterior

single-tooth implants with a 1.5 mm smooth neck, a moderately rough neck with

grooves and with a scalloped moderately rough neck with grooves in preserving

marginal bone as measured on radiographs. This effect can be attributed entirely

to the implants with a scalloped neck, showing significantly more marginal bone

loss than the other implant designs studied. Furthermore, deeper probing pock-

ets depths and more bleeding were observed around these implants. Post-hoc

analyses revealed no differences between the implants with a smooth neck and

implants with a moderately rough neck with grooves in preserving marginal bone,

and no differences in survival, soft tissue aspects and complications. Besides,

these implants showed favorable results as compared to what has been estab-

lished in other studies on anterior single-tooth implants. We therefore suggest

the use of either an implant with a 1.5 mm smooth neck or an implant with a

moderately rough neck with grooves for replacement of a single missing anterior

tooth as the scalloped implant design showed more bone loss and less favorable

clinical performance.

1.5 mm smooth collar. We observed a mean bone loss of 2.0 ± 0.77 mm around

the scalloped neck after 18 months, although it was equipped with a moderately

rough surface and grooves, which could favor marginal bone preservation.

We do not have a proper explanation for the finding that the scalloped implant

showed more radiographic bone loss than the other study groups. One reason

might be that peri-implant bone is mainly formed in a horizontal plane. As a re-

sult, bone at the proximal side of the implant might tend to be lost to equilibrate

the more apical level of the mid-facial and mid-palatal peri-implant bone crest.

Another reason could be inferred from a biomechanical point of view. Too much

stress at the implant neck after loading, and shear stresses in particular, induces

initial marginal bone resorption (Oh et al. 2002; Schrotenboer et al. 2008). It has

been hypothesized that after this initial resorption, bone loss slows down at the

first thread when shear stresses change into more favorable compressive forces

induced by the thread itself (Oh et al. 2002). It might be that the stress distribu-

tion from the scalloped implant to the bone was unfavorable and too high, lead-

ing to the amount of marginal bone loss as was observed during the first evalu-

ation period. In this context, the complex connection between implant and abut-

ment could play a role. However, stress models of scalloped implants are lacking.

We do not feel that the radiographic analysis had shortcomings in detecting the

small and less dense proximal bone peak around the scalloped implant, as has

been suggested in some studies (Wohrle 2006; McAllister 2007). In this view, the

clinical observation of deeper probing pocket depths can be adduced.

As was expected from other studies (Cardaropoli et al. 2006; Den Hartog et

al. 2008; Meijndert et al. 2008; Bratu et al. 2009; Nickenig et al. 2009), the most

extensive marginal bone loss was observed during the first evaluation period (i.e.,

from implant placement to T6m

). During the next 12 months (at T18m

), only minor

marginal bone loss was noticed. This is consistent with the stable level of the

mid-facial peri-implant mucosa as measured during the second evaluation pe-

riod. The level of the papilla, however, was not stable but gained some height.

Expressed in papilla index scores, this resulted in higher scores at T18m

compared

to T6m

for all implant groups. This phenomenon has been reported in several

single-tooth implant studies reporting comparable papilla index scores (Jemt &

Lekholm 2003, Schropp et al. 2005a; Den Hartog et al. 2008; Meijndert et al.

2008). Neither from these studies nor from the current study could this phenom-Neither from these studies nor from the current study could this phenom-

enon be validly explained.

Within the whole study population, the changes in marginal peri-implant bone

level were not correlated with the volume of the papilla expressed in papilla index

scores neither with the facial peri-implant mucosal level (PML) compared to the

contralateral tooth. At T18m

, the scalloped group did not show lower volume of the

papilla expressed in papilla index scores and no higher discrepancies in PML than

Cha

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Impl

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62 63

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This is an edited version of the manuscript: Den Hartog, L., Raghoebar, G.M., Huddleston Slater,

J.J., Stellingsma, K., Vissink, A., Meijer, H.J. Single-tooth implants in the aesthetic zone with dif-

ferent neck designs: a randomized clinical trial to the evaluating aesthetic outcome

(submitted for publication, 2010).

4.


the aesthetic zone: a randomized clinical trial evaluating the aesthetic

outcome

Cha

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ant n

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4

66 67

AbstrAct

Aim: To evaluate the aesthetic outcome of single-tooth implants in the aes-To evaluate the aesthetic outcome of single-tooth implants in the aes-

thetic zone with different neck designs from a professional’s and patient’s

perception.

Material and Methods: 93 patients with a missing anterior tooth in the maxil-

la were randomly assigned to be treated with an implant with a smooth

neck, a rough neck with grooves or a scalloped rough neck with grooves.

Implants were installed in healed sites. One year after definitive crown pla-

cement, photographs were taken and the aesthetic outcome was assessed

by professionals according to two objective aesthetic indexes (PES/WES

and Implant Crown Aesthetic Index (ICAI)). A questionnaire was used to

assess the aesthetic outcome and general satisfaction from a patient’s per-

ception.

Results: One implant was lost. There were no differences in aesthetic out-

come between the implant neck designs. According to the professional’s

assessment using PES/WES and ICAI, respectively 79.3% and 62% of the

cases showed acceptable crown aesthetics and 59.8% and 56.5% accept-

able mucosa aesthetics.

Overall, patients were satisfied about the aesthetics of the mucosa (>80%)

and crown (>93%) and general patient satisfaction was high (9.0 ± 1.0)

out of a maximum of 10). The professional’s assessment revealed that a

pre-implant augmentation procedure was associated with less favorable

aesthetics of the mucosa.

Conclusion: This study shows that the aesthetic outcome of single-tooth

implants in the maxillary aesthetic zone appears to be independent on the

implant neck designs applied, but dependent on the need for pre-implant

surgery.

IntroductIon

The focus of attention in contemporary implantology has shifted from implant

survival towards the quality of implant survival. Particularly in the anterior region,

the aesthetic outcome has been considered to be of significance for the overall

treatment success (Den Hartog et al. 2008, Annibali et al. 2009, Belser et al.

2009). Both the appearance of the implant crown and the peri-implant mucosa

contribute to the final aesthetic outcome (Meijer et al. 2005, Belser et al 2009).

The level of the peri-implant mucosa is an important aspect determining the

aesthetic outcome (Meijer et al. 2005, Belser et al 2009). The level of the peri-im-

plant marginal bone has been associated with the level of the peri-implant muco-

sa (Bengazi et al. 1996, Hermann et al. 1997, Hermann et al. 2001). After implant

placement, it is accepted that some peri-implant marginal bone loss will occur

(Laurell et al. 2009). Hence, loss of peri-implant marginal bone might affect the

level of the peri-implant mucosa and with that the final aesthetic outcome.

The design of the implant neck is considered to be of relevance for preserva-

tion of marginal peri-implant bone (Hermann et al. 1997, Lee et al. 2007, Bratu et

al. 2009). It has been reported that an implant neck with a roughened surface or

with retention elements might result in less marginal peri-implant bone resorp-

tion than a traditional smooth implant neck. (Shin et al. 2006, Lee et al. 2007,

Bratu et al. 2009) As a consequence, novel implant designs are often provided

with a roughened surface and retention elements at the implant neck to induce

maximum bone preservation, particularly when to be applied in aesthetically sen-

sitive cases. Apart from the capacity of a rough implant neck to preserve marginal

peri-implant bone, it has been suggested that an implant neck with a scalloped

implant platform might preserve marginal peri-implant bone, particularly at the

proximal side (Wohrle et al. 2003, Kan et al. 2007). Such a scalloped implant neck

would mirror the alveolar ridge curvature, which is lower on the facial and oral

aspects but rises in the proximal areas. As a consequence, a more non-violant

position of the implant-abutment interface could be realised compared to com-

mon flat-platform implant designs.

To assess the aesthetic outcome of implant therapy, both the opinion of the

professional and patient have to be considered. From a professional’s perception,

the aesthetic outcome should be explored using an objective rating instrument.

Such an instrument will facilitate a thorough analysis of the final result to improve

surgical or prosthetic treatment aspects. Furthermore, it can be of value to assess

treatment strategies longitudinally or to identify host factors. Recently, two instru-

ments have been introduced to measure the aesthetics of the crown and mucoca,

namely The Implant Crown Aesthetic Index (ICAI) (Meijer et al. 2005) and the

Pink Esthetic Sore/White Esthetic Score (PES/WES) (Belser et al. 2009).

As the patient is the final user of implant therapy, the opinion of the patient

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is also of importance (Esposito et al., 2009). A method to assess the subjective

aesthetic outcome from a patient’s perspective is the use of questionnaires (Levi

et al. 2003, Schropp et al. 2004, Pjetursson et al. 2005).

Inherent to the recent shift in implantology towards the quality of implant sur-

vival, only a few studies on implant therapy in the anterior dentition inquired into

the aesthetic outcome (Den Hartog et al. 2008, Annibali et al. 2009). To our best

knowledge, no clinical trials have yet been published addressing the aesthetic out-

come of different implant neck designs. Furthermore, little is known about predis-

posing factors associated with the final aesthetic outcome. Therefore, the aim of

this trial was to assess from a professionals and patient’s perception, the aesthetic

outcome of anterior single-tooth implants with three different neck designs.


PatientsAll patients with a single missing tooth in the maxillary aesthetic zone (incisor,

canine or first premolar) who were referred for implant treatment to the depart-

ment of Oral and Maxillofacial Surgery (University Medical Center Groningen,

University of Groningen, Groningen, the Netherlands) were considered for inclu-

sion. Patients had to be at least 18 years of age. The width of the diastema was

at least 6 mm and was neighboured with natural teeth. Oral hygiene had to be

adequate (modified plaque index and modified sulcus bleeding index scores ≤ 1

(Mombelli et al. 1987). Exclusion criteria were smoking, ASA score ≥ III, presence

of an active periodontal disease as expressed by probing pocket depths ≥ 4 mm

and bleeding on probing (index score > 1) and a history of radiotherapy to the

head and neck region.

Study designThe study protocol of this prospective randomized clinical trial was approved

by the Medical Ethical Committee of the University Medical Center Groningen

and written informed consent was obtained from all eligible patients before en-

rolment. Patients were included between January 2005 and February 2008. By

means of a specifically designed locked computer program, patients were ran-

domly assigned to one of three study groups to be treated with an implant with

a 1.5 mm smooth (‘machined’) implant neck (Replace Select Tapered, Nobel -

Biocare AB, Göteborg, Sweden) – ‘smooth’ group;

a rough implant neck with grooves (NobelReplace Tapered Groovy, Nobel -

Biocare AB) – ‘rough’ group;

a scalloped rough implant neck with grooves (NobelPerfect Groovy, Nobel -

Biocare AB) – ‘scalloped’ group.

Randomization by minimization (Altman 1991) was used to minimize differ-minimize differ-

ences between the treatment groups with regard to the following variables: age

(≤30 years, >31 ≤ 60 years, > 60 years), location of the implant site (central or lat-

eral incisor, canine or first premolar) and whether or not a pre-implant augmenta-

tion procedure in a separate session was indicated beforehand. The surgeon that

inserted the implants was informed about the allocation on the day of surgery.

Intervention procedureImplants were inserted in healed sites at least three months after tooth removal.

When bone volume was insufficient for implant placement, a bone augmentation

procedure was carried out in a separate session. As a grafting material, autoge-

nous intra-oral bone was used together with anorganic bovine bone (Geistlich

Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland). Implants were inserted

three months after the augmentation procedure.

At implant surgery, a slightly palatal crest-incision with extensions through the

buccal and palatal sulcus of the adjacent teeth and a divergent relieving incision at

the distal tooth were made. A minimal mucoperiosteal flap was prepared to expose

the alveolar ridge. The implant site was prepared by using a surgical template that

was fabricated in the dental laboratory, based on the prospective implant crown in

its ideal position. The shoulder of the implant was placed at a depth of 3 mm apical

to the most apical aspect of the surgical template for optimal emergence profile.

For the scalloped implants the mid-facial part of the implant shoulder was taken

as reference. In all cases the alveolar bone was levelled to the implant neck. An im-

plant dehiscence, fenestration or bone wall thickness <2mm facially to the implant,

was augmented according to a local augmentation procedure with autogenous

bone chips collected during implant bed preparation and anorganic bovine bone

(Geistlich Bio-Oss®) covered with Geistlich Bio-Gide®. The wound was closed with

Ethilon 5-0 nylon sutures (Johnson & Johnson Gateway, Piscatatway, USA).

During the healing phase, patients were wearing a removable partial denture

that did not interfere with the wound. After three months, implants were un-

covered and a screw-retained provisional crown was fabricated by means of an

engaging temporary abutment and composite (Solidex, Shofu inc., Kyoto, Japan).

After a provisional phase of three months (i.e., six months post-implant place-

ment) a definitive crown was made consisting of an individually fabricated zirco-

nia abutment for the smooth and rough groups (Procera, Nobel Biocare AB) and

individualized titanium abutments (Procera, Nobel Biocare AB) for the implants

in the scalloped group, since zirconia abutments were not available for these im-

plants. A zirconica Procera coping (Nobel Biocare AB) was luted over the titani-

um abutments in order to create an abutment with a zirconia outside. Depending

on the location of the screw access hole, crowns were cement-retained by means

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Measurements were done by two observers that were blinded to the group al-

location. The intra-observer agreement of the ICAI and PES/WES has been shown

to be acceptable in the studies in which these indexes were introduced (Meijer et

al 2005, Belser et al. 2009).

Patient satisfactionPatient satisfaction was assessed using a self-administered questionnaire. The

questionnaire comprized of four questions regarding patient’s aesthetic satisfac-

tion with the colour and shape of the crown and mucosa. These questions could

be answered on a 5-point rating scale ranging from ‘very dissatisfied’ (score 1) to

‘very satisfied’ (score 5). Furthermore, patients were asked to mark their general

satisfaction on a 10 cm Visual Analogue Scale (VAS) having end phrases ‘very dis-

satisfied’ (0) on the left end and ‘very satisfied’ (10) on the right end.

Data analysisICAI crown scores, ICAI mucosa scores, PES scores and WES scores were ana-

lyzed separately. To assess the inter-observer agreement of both aesthetic evalu-

ation instruments, linear weighted kappa (κ) values were calculated. Per patient,

ICAI and PES/WES scores of both observers were averaged. For the ICAI, the

average score was subsequently transposed to the corresponding judge (i.e. ex-

cellent, satisfactory, moderate, poor aesthetics).

For between-group comparisons Kruskal-Wallis tests were used followed by

post-hoc Mann-Whitney tests in case of statistical significance. To identify fac-identify fac-

tors associated with the aesthetic outcome, regression analyses were performed.

The following factors were explored: implant type, age, gender and whether or

not a pre-implant augmentation procedure was performed. Correlations between

the aesthetic outcome and patient’s aesthetic satisfaction were determined with

Spearman’s correlation tests.

In all analyses, a significant level of 0.05 was chosen. Data were analysed using

the Statistical Package for Social Sciences (version 16.0, SPSS Inc, Chicago, USA).

results

PatientsA total of 93 patients was included. Details regarding patient characteristics are

depicted in Table 1. One implant in the smooth group was lost five months after

implant placement. The implant survival rate at 18 months after implant place-

ment was 96.8 % (1 implant lost) for the smooth group and 100% for the rough

and scalloped study groups. All patients attended the follow-up visit at one year

after definitive crown placement.

of a zirconia Procera coping (Nobel Biocare AB) or screw-retained by fusing por-

celain directly to the abutment. Cemented-retained crowns were cemented with

glass ionomer cement (Fuji Plus, GC Europe, Leuven, Belgium). In seven patients

the contralateral tooth received a new all-ceramic zirconia crown (Procera) in the

same procedure (two in the smooth group and rough group, three in the scal-

loped group). For more details regarding product specifications, we refer to a

previous clinical report (Den Hartog et al. 2009).

All surgical procedures were performed by a single experienced surgeon. The

prosthetic procedure was accomplished by two experienced prosthodontists and

all crowns were fabricated by one dental technician.

Aesthetic assessmentThe aesthetic outcome was assessed on digital photographs that were taken one

year after placement of the definitive crown (18 months after implant placement)

(camera: Fuji-film FinePix S3 Pro). The implant and adjacent dentition were cap-

tured on one photograph which was centered at the midline. Of implants that

replaced a lateral incisor, canine or first premolar, two additional photographs

were taken on which the implant and contralateral tooth were centered.

The Implant Crown Aesthetic Index (ICAI) (Meijer et al. 2005) and the Pink Es-

thetic Sore/White Esthetic Score (PES/WES) (Belser et al. 2009) were used to de-

termine the aesthetics of the peri-implant mucosa and implant crown. Both index-

es were used, to allow for comparison with data from other studies. Both indexes

are composed of aesthetically related items based on the anatomic form, colour

and surface characteristics of the implant crown and peri-implant soft tissue.

The ICAI contains nine items, of which five related to the crown and four relat-

ed to the peri-implant mucosa. For each item, penalty points of 0, 1 and 5 can be

given representing respectively no, minor and major deviations compared to the

contralateral tooth and adjacent dentition. The total score for crown and mucosa

leads to the following corresponding judgement about the aesthetic outcome: 0

points, excellent; 1 or 2, satisfactory; 3 or 4, moderate; 5 or more, poor aesthetics

(note: one item with a major deviation leads to poor aesthetics). In this study,

the ICAI was slightly modified and has been used to analyze the aesthetics of the

crown (ICAI crown) and the aesthetics of the mucosa (ICAI mucosa) separately.

The PES/WES contains ten items, five for crown and mucosa each. In contrast

to the ICAI, the PES/WES reward items with points instead of utilizing penalty

points. Taking the contralateral tooth as a reference, on each item 0, 1, or 2 points

can be assigned representing major, minor or no discrepancies respectively. The

highest possible score for the crown (WES) and for the mucosa (PES) is 10. A

threshold of clinical acceptability has been defined for the PES/WES, which is set

at 6 points for the WES and 6 points for the PES.

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The factor age contributed significantly to the outcome of WES (regression coef-

ficient -0.048), whereas implant type and gender were not associated with the

aesthetic outcome.

Patient satisfactionPatient satisfaction was high (Table 3) and there were no between-group differ-

ences. General patient satisfaction scores using VAS ranged from 5.5 to 10.

Patient’s aesthetic satisfaction with the appearance of the mucosa (colour and

shape) was correlated with the outcome of PES. The outcome of all questions

was correlated with general patient satisfaction.

dIscussIon

This clinical trial assessed the aesthetic outcome of single-tooth implants in the

anterior dentition with three different neck designs as an independent factor,

Aesthetic assessmentsThe PES/WES showed a satisfactory inter-observer agreement. A weighted

κ-value of 0.69 was calculated for the PES and a value of 0.62 for the WES. The

ICAI showed satisfactory inter-observer agreement for the soft tissue assessment

(κ-value 0.64), whereas moderate agreement was found for the assessment of

the crown (κ-value 0.39). Because of this moderate agreement, the ICAI crown

assessment was not used in the statistical analyses.

There were no differences between study groups regarding the aesthetic out-

come of the crown and peri-implant mucosa (Table 2). Furthermore, a per-item

analysis of both indexes showed no differences between study groups. According

to the PES/WES, in 59.8 % of the cases the mucosa showed acceptable aesthet-

ics (PES-score ≥ 6) and in 79.3% of the cases the aesthetics of the crown were

acceptable (WES-score ≥ 6). According to the ICAI, 56.5% of the cases showed

satisfactory mucosa aesthetics (satisfactory and excellent) and 62% showed sat-

isfactory crown aesthetics. For both indexes, the crown item ‘colour of the crown’

showed the lowest score and most penalty points. According to the WES, 69%

of the crowns showed a discrepancy in colour and according to the ICAI this

percentage was 68% (mean values of both observers). The soft tissue item ‘level

of the facial mucosa’ showed the most penalty points of the ICAI (54 % on aver-

age showed deviation) and the second lowest score of the PES (61% on average

showed deviation). The PES-item ‘root convexity, soft tissue colour and texture’

was assigned the lowest score (76% showed deviation).

Multivariate linear regression analysis revealed that a pre-implant augmen-

tation procedure was significantly associated with a lower PES score and ICAI

mucosa score (regression coefficient respectively 1.27 and 0.55 for PES and ICAI).

Table 1. Baseline characteristics per study group.

VariableSmooth group

(n=31)

Rough group

(n=31)

Scalloped group

(n=31)

Mean age (years) ± standard deviation Range (years)

37.2 ± 12.9 (18-60) 40.1 ± 14.4 (18-67) 40.1 ± 17.2 (19-80)

Male/female ratio 15/16 17/14 14/17

Implant site location I1 / I2 / C / P1

20 / 7 / 1 / 3 18 / 8 / 3 / 2 18 / 6 / 3 / 4

Augmentation before implant surgery*

12 11 10

*Implants were installed after three months.

Table 2. PES, WES, ICAI mucosa and ICAI crown scores per study group and for the whole study population.

Smooth(n=30)†

Rough(n=31)

Scalloped(n=31)

Overall(n=92)

PES Mean ± SD Range

6.0 ± 1.91.5 - 9.5

6.3 ± 1.73.5 - 9.5

6.6 ± 1.63.5 - 9

6.3 ± 1.71.5 - 9.5

WES Mean ± SD Range

7.2 ± 1.54.5 - 9.5

7.4 ± 1.64 - 10

7.2 ± 1.64.5 - 10

7.3 ± 1.54 - 10

ICAI Mucosa Excellent Satisfactory Moderate Poor

2 (6.7%)14 (46.7%)8 (26.7%)6 (20%)

0 (0%)15 (48.4%)6 (19.4%)10 (32.3%)

0 (0%)21 (67.7%)4 (12.9%)6 (19.4%)

2 (2.2%)50 (54.3%)18 (19.6%)22 (23.9%)

ICAI Crown Excellent Satisfactory Moderate Poor

1 (3.3%)17 (56.7%)10 (33.3%)2 (6.7%)

1 (3.2%)18 (58.1%)10 (32.3%)2 (6.5%)

1 (3.2%)19 (61.3%)7 (22.6%)4 (12.9%)

3 (3.3%)54 (58.7%)27 (29.3%)8 (8.7%)

†One implant was lost.

Abbreviations: SD=Standard deviation, PES=Pink Esthetic Score, WES=White Esthetic

Score, ICAI=Implant Crown Aesthetic Index.

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using two established indexes for rating the objective aesthetic outcome and a

questionnaire to subjectively evaluate the aesthetics from the patient’s percep-

tion. No differences were observed between the aesthetic outcome of the three

implant neck designs included in this trial. Patient satisfaction was high and it

revealed that there was a discrepancy between the patient’s aesthetic satisfaction

and the objective aesthetic outcome according to the indexes.

With regard to the aesthetic outcome of the peri-implant mucosa, no differ-

ences were notified between the three implant neck designs. Furthermore, none

of the separate soft tissue items showed differences between the study groups.

Beforehand, we hypothesized that the design of the implant neck might have

an effect on the level of the peri-implant mucosa. However, using both indexes,

such an effect could not be shown in our study. One reason for this might be

that the difference in marginal bone resorption between the scalloped group and

the other study groups brought about a clinical effect that was too little to be

observed with the aesthetic indexes we applied (See Chapter 3 for more details

regarding marginal bone loss). A second reason might be attributed to the role

of the periodontium of the adjacent teeth. It is assumed that the bone level next

to the adjacent teeth is highly related to at least the future level of the papillae

(Choquet et al. 2001, Romeo et al. 2008). Possibly, the periodontium also acts on

other aesthetically related aspects as the level of the facial mucosa.

The aesthetic assessment of the crown did not reveal differences between

study groups. We believe that the implant neck designs we investigated are of

less importance for the final crown aesthetics. Implants in the study groups were

restored according to the same procedure. The only difference was that for the

implants in the scalloped group, titanium abutments had to be used instead of

zirconia abutments in the smooth and rough group. However, the titanium abut-

ments were modified by means of a zirconia layer. Besides, all crowns in this

study were all-ceramic.

As a result from the recent introduction of the PES/WES and ICAI, published

studies using these indexes for aesthetic evaluation are scarce. Only two studies

could be identified that reported the aesthetic outcome of anterior single-tooth

replacements using the PES/WES (Belser et al. 2009, Buser et al. 2009) and only

one study using the ICAI (Meijndert et al. 2007). To our best knowledge, these are

the only available instruments to rate the aesthetics of both crown and mucosa.

In the first study on the PES/WES (Belser et al. 2009), the reproducibility of this

index was analyzed on the basis of 45 maxillary single-tooth implants installed

according to an early implant placement procedure. A mean PES-score of 7.7 ±

1.3 was reported and no implant scored lower than 6 points, the predefined level

of clinical acceptability. In a second study from the same research group (Buser

et al. 2009), a PES-score of 8.1 ± 1.75 was reported for 20 early placed implants

and only one case showed less than 6 points. In our study, the aesthetics of the

mucosa were judged with a mean score of 6.3 and 40.2 % of the cases scored less

than 6 points, thus were clinical unacceptable. Most likely, a less favorable pre-

operative situation was the underlying factor for these lower PES-scores. In our

study, all implants were inserted in healed extraction sites and teeth had already

been extracted at the first consultation without having opportunities to perform

socket preservation techniques. It is known that after tooth removal, the walls

of the alveolus undergo substantial resorption at the facial aspect, affecting the

soft tissue anatomy (Schropp et al. 2003, Araujo & Lindhe 2005). Early implant

placement and simultaneous guided bone regeneration according to which the

implants in the abovementioned studies were inserted, might favor the facial soft

tissue anatomy. For instance, it was demonstrated in these studies that the level

of the contralateral reference tooth was identical in 77.8 % (35 of 45) (Belser et al.

2009) and 90% (18 of 20) (Buser et al. 2009) of the cases. In our study however,

this item showed the second lowest score of all items and in 36 of 92 patients

(39%) the level of the mucosa was identical.

The less favorable preoperative situation in our study is also reflected in the

frequency of pre-implant augmentation procedures, necessary to allow for proper

implant installation three months later. In our study, a pre-implant augmentation

procedure was needed in one-third of the patients and the regression analysis

showed that this procedure was significantly associated with a lower PES-score. A

Table 3. Patient satisfaction per study group and for the whole study population.

Number of patients being satisfied (%)*

Smooth(n=30)†

Rough(n=31)

Scalloped(n=31)

Overall

Colour of the crown 28 (93.3%) 30 (96.8%) 28 (90.0%) 86 (93.3%)

Form of the crown 28 (93.3%) 31 (100%) 29 (93.5%) 88 (95.7%)

Colour of the mucosa around the implant

26 (86.7%) 27 (87.1%) 26 (83.9%) 79 (85.9%)

Form of the mucosa around the implant

24 (80.0%) 27 (87.1%) 24 (77.4%) 75 (81.5%)

General patient satisfaction (VAS-score; mean ± SD)

8.8 ± 1.1 8.9 ± 1.0 9.1 ± 0.8 9.0 ± 1.0

*Measured on 5-point scale (4 or 5 equals satisfied and very satisfied respectively) †One implant was lost.

Abbreviations: SD=standard deviation, VAS=visual analogue scale.

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thetic outcome according to an objective index is poor. The aesthetic indexes do

not take the preoperative situation into account.

With respect to the reproducibility of the ICAI, controversial degrees of in-

tra- and interobserver agreement have been reported. At the introduction of the

ICAI, two prosthodontists showed acceptable intra- and interobserver agreement.

Gehrke et al. (Gehrke et al. 2009), however, reported poor to moderate reliabil-

ity for the ICAI when applied by different professionals including prosthodon-

tists. In our study, the ICAI was slightly modified and was used to generate a

separate judgment for the crown and mucosa instead of an overall judgement.

It was found that the reliability of the mucosa assessment was acceptable and

of the crown assessment was moderate. Apparently, the crown is more prone

to disagreement than the mucosa. We believe that this moderate reproducibility

might be caused by the scoring system of the ICAI and the corresponding final

judgement. Namely, when an item deviates majorly in the observer’s eyes, the

aesthetics will be judged automatically as being poor. However, when this devia-

tion is minor according to another observer, large differences in final judgment

will occur. Furthermore, the ICAI is based on comparing the implant crown with

the contralateral tooth and the adjacent dentition as well. This might lead to more

variation in observer interpretation. Since the PES/WES applies a different scor-

ing system and the contralateral tooth is the only reference, this index might be

less sensitive for disagreement and subsequently showed higher reliability. How-

ever, this might also lead to shortcomings, since a major discrepancy on an item

yet might lead to acceptable aesthetics and in some cases it would be more plau-

sible to involve the adjacent dentition in the analyses as well (for instance when

the contralateral tooth shows compromised aesthetics). More studies would be

helpful to further develop a reproducible and valid aesthetic index, which should

be commonly applied in implant research.

This study shows that at one year after definitive crown placement, there are

no differences in aesthetic outcome between the different implant necks of sin-

gle-tooth implants applied in the aesthetic zone. According to the most repro-

ducible index (the PES/WES), the peri-implant mucosa was judged as being not

acceptable in 40% of the cases whereas 20% of the implant crowns were not ac-

ceptable. However, patient’s aesthetic satisfaction regarding colour and shape of

crown and mucosa was high. It should be realized that in this study all implants

were installed in healed sites, at least three months after extraction and one third

of the cases had to be augmented before implant placement. Since we found that

a pre-implant augmentation procedure has a detrimental effect on the objective

aesthetic outcome (using PES/WES), this underlines the need to prevent a sepa-

rate augmentation procedures, possibly by extracting hopeless teeth in an earlier

stage or by performing socket preservation techniques.

study to the aesthetic outcome of anterior single-tooth implants installed after a

separate augmentation procedure, confirmed the negative effect of a pre-implant

placement augmentation procedure on the appearance of the mucosa (Meijndert

et al. 2007).

With regard to the assessments of the implant crown, in the study by Belser

et al. (2009) crowns were judged with a mean WES-score of 6.9 ± 1.5 which is in

line with the score of 7.3 ± 1.5 as we observed. However, in the other study from

the same research group, the mean WES-score was 8.7 ± 1.0. It was argued that

this higher WES-score could be explained by the fact that only one dental techni-

cian was involved having excellent expertise in the field of esthetic restorations

versus multiple joining technicians in the other study. Compared to our study,

this difference in white aesthetics might be explained from the fact that in our

study the contralateral tooth received a new crown less frequently (in the study by

Buser et al. (2009), 5 of 20 contralateral teeth received a new crown, in our study

7 of 92). Since the contralateral tooth serves as a reference tooth in assessing the

white aesthetics, it is easier to reach a higher aesthetic judge when these teeth

are provided with a new crown too, particularly on the variables colour, translu-

cency and texture. Furthermore, it should be realized that the less favorable pink

aesthetics we observed, could affect the outcome of the white aesthetics. Less

voluminous papillae for instance or an undercontoured alveolar process might be

compensated by overcontouring the anatomy of the crown. Regarding the colour

of the crown, this will remain a challenging item to fulfil without any discrepancy.

In our study and in the study by Buser et al. (2009), this item showed the lowest

appreciation. It should be realized however that the aesthetics were assessed on

photographs. It might be that in a direct assessment of the patient, the colour of

the crown shows more favorable resemblance with the adjacent dentition.

As was expected from other studies, patient satisfaction was high (Schropp et

al. 2004, Pjetursson et al. 2005, Den Hartog et al. 2008). Although the outcome

of PES was correlated to patient satisfaction with the appearance of the mucosa,

most of the patients were satisfied with the appearance of the mucosa (> 80%)

and even more patients were satisfied with the appearance of the crown (> 93%).

This discrepancy between the aesthetic outcome from a professional’s and pa-

tient’s perception, has been demonstrated in earlier studies (Chang et al. 1999,

Meijndert et al. 2007, Esposito et al 2009). This difference might be explained by

the finding that factors considered by professionals to be relevant for the esthetic

outcome may not be of decisive importance for patient’s aesthetic satisfaction.

(Chang et al. 1999) Furthermore, it might be that for the final appreciation of the

patient, the pre-operative situation plays a role of significance and gives weight

to the final judgment. When the pre-operative situation is compromized and pa-

tient’s expectations are realistic, patients might be satisfi ed even when the aes-might be satisfied even when the aes-

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References

Annibali, S., Bignozzi, I., La Monaca, G. & Cristalli, M.P.

(2009) Usefulness of the Aesthetic Result as a Success

Criterion for Implant Therapy: A Review. Clinical Implant

Dentistry and Related Research

Araujo, M.G. & Lindhe, J. (2005) Dimensional ridge altera-

tions following tooth extraction. An experimental study in

the dog. Journal of Clinical Periodontology. 32, 212-218.

Belser, U.C., Grutter, L., Vailati, F., Bornstein, M.M., Weber,

H.P. & Buser, D. (2009) Outcome evaluation of early placed

maxillary anterior single-tooth implants using objective

esthetic criteria: a cross-sectional, retrospective study in 45

patients with a 2- to 4-year follow-up using pink and white

esthetic scores. Journal of Periodontology 80, 140-151.









Buser, D., Halbritter, S., Hart, C., Bornstein, M.M., Grutter,

L., Chappuis, V. & Belser, U.C. (2009) Early implant place-

ment with simultaneous guided bone regeneration follow-

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results of a prospective study with 20 consecutive patients.


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(1999) Esthetic outcome of implant-supported single-tooth

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Esposito, M., Grusovin, M.G. & Worthington, H.V. (2009)

Pjetursson, B.E., Karoussis, I., Burgin, W., Bragger, U. &

Lang, N.P. (2005) Patients’ satisfaction following implant

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Schropp, L., Isidor, F., Kostopoulos, L. & Wenzel, A. (2004)

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Schropp, L., Wenzel, A., Kostopoulos, L. & Karring, T.

(2003) Bone healing and soft tissue contour changes follow-

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This is an edited version of the manuscript: Den Hartog, L., Raghoebar, G.M., Stellingsma, K.,

Vissink, A., Meijer, H.J. Immediate loading of single implants in the aesthetic zone: a randomized

clinical trial. Journal of Clinical Periodontology (accepted for publication, 2010)

5.

Immediate loading of single-tooth implants in

the aesthetic zone: a randomized clinical trial

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AbstrAct

Aim: To compare the outcome of immediate loading with conventional

loading for single-tooth implants in the maxillary aesthetic zone. It was

hypothesized that immediate loading is not inferior to conventional load-

ing.

Materials and Methods: 62 patients with a missing maxillary anterior tooth

were randomly assigned to be treated with an implant that was either re-

stored with a non-occluding temporary crown within 24 hours after implant

placement (‘immediate group’) or was restored according to a two-stage

procedure after three months (‘conventional group’). All implants were

installed in healed sites. Follow-up visits were conducted after 6 and 18

months post-implant placement. Outcome measures were radiographic

marginal bone level changes, survival, soft tissue aspects (probing depth,

plaque, bleeding, soft tissue level), aesthetics and patient satisfaction.

Results: No significant differences were found between both study groups

regarding marginal bone loss (immediate group 0.91±0.61 mm, conven-

tional group 0.90±0.57 mm), survival (immediate group 96.8%: 1 implant

lost, conventional group 100%), soft tissue aspects, aesthetic outcome

and patient satisfaction.

Conclusion: Within the limitations of this study (sample size, follow-up du-

ration) it can be concluded that, for single-tooth implants in the anterior

maxilla, the outcome of immediate loading is not less favorable than con-

ventional loading.

IntroductIon

Dental implants are commonly applied to replace missing teeth. Traditionally,

implants were subjected to a load-free healing period of several months, allowing

the implant to osseointegrate without being exposed to external forces. Over the

last years, the concept of immediate loading has gained attention. This concept

is defined as the application of a load by means of a restoration within 48 hours

after implant placement (Laney 2007).

Patients with a missing anterior tooth may benefit from immediate loading.

Placement of the (provisional) implant crown immediately after implant place-

ment reduces overall treatment time, avoids a second-stage operation and offers

immediate comfort as there is no need for a provisional removable prosthesis

during the healing phase.

Besides the beneficial effects of immediate loading, this concept has also

some inherent thought disadvantages. E.g., immediate loading might induce mi-

cromotion and instability of the implant (Gapski et al. 2003, Trisi et al. 2009).

Implant instability might result in fibrous encapsulation of the implant and failing

osseointegration (Lioubavina-Hack et al. 2006). Albeit yet applied on implants

placed in mandibles to support bridges or bar-retained overdentures (Esposito

et al. 2009), immediate loading of maxillary single-tooth implants might involve

more risk. The quality of bone is poorer in the maxilla than in the mandible in the

context of achieving primary implant stability (Mesa et al. 2008, Trisi et al. 2009,

Roze et al. 2009). Thus implants in this region might be more susceptible to mi-

cromotion. Furthermore, force distribution to other implants by splinting is not

possible for single-tooth implants.

In contrast to the mandible, well-designed clinical trials on immediate load-

ing of single-tooth implants in the anterior maxilla are scarce (Den Hartog et al.

2008, Esposito et al. 2009, Grutter & Belser 2009) and there is limited evidence

regarding the effect of immediate loading on peri-implant marginal bone and soft

tissue responses (Glauser et al. 2006, Den Hartog et al. 2008, Grutter & Belser

2009). Therefore, the aim of this study was to compare the outcome of immedi-

ate loading with that of conventional loading of implants applied for a missing

anterior maxillary tooth. It was hypothesized that immediate loading is not infe-

rior to conventional loading.


PatientsPatients referred to the department of Oral and Maxillofacial Surgery (Univer-

sity Medical Center Groningen, University of Groningen, Groningen, the Nether-

lands) for anterior single implant treatment were considered for inclusion

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if they fulfilled the following criteria:

at least 18 years of age;-

one missing tooth being an incisor, canine or first premolar in the maxilla -

with adjacent natural teeth;

adequate oral hygiene, i.e. modified plaque index score and modified sulcus -

bleeding index score ≤ 1 (Mombelli et al. 1987);

mesial-distal width of diastema at least 6 mm; -

vertical occlusal dimensions allow for creation of a non-occluding provision--

al crown.

Exclusion criteria were:

ASA score ≥ III (Smeets et al. 1998);-

presence of active clinical periodontal disease as expressed by probing pock- as expressed by probing pock--

et depths ≥ 4 mm and bleeding on probing;

presence of peri-apical lesions or any other abnormalities in the maxillary -

anterior region as determined on a radiograph;

smoking; -

a history of radiotherapy to the head and neck region.-

Study designThis randomized clinical trial was approved by the ethics committee of the Uni-

versity Medical Center Groningen. A written informed consent was obtained from

patients before enrollment. Patients were included between January 2005 and

February 2008.

A specifically designed locked computer software program was used to ran-

domly assign patients to one of two study groups to receive an implant with an

anodized surface (NobelReplace Tapered Groovy, Nobel Biocare AB, Göteborg,

Sweden) that was either restored within 24 hours after implant placement (‘im-

mediate group’) or was restored according to a two-stage procedure after three

months of healing (‘conventional group’). Randomization by minimization (Alt- Randomization by minimization (Alt-

man 1991) was used to balance possible prognostic variables between the treat-

ment groups. Minimization was used for the variables age (≤30 years, >31 ≤ 60

years, > 60 years), location of the implant site (central or lateral incisor, canine or

first premolar) and whether or not a pre-implant augmentation procedure was in-

dicated based on a clinical and diagnostic cast assessment. The allocation result

was kept in a locked computer file that was not accessible for the examiner and

the practitioners. The surgeon that inserted the implants was informed about the

allocation on the day of surgery.

InterventionsAll implants were placed in healed sites at least three months after tooth remov-

al, allowing the extraction site to heal. When bone volume was insufficient for

implant insertion, a bone augmentation procedure was carried out. As a graft-

ing material, autogenous bone was used together with anorganic bovine bone

(Geistlich Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland) covered with

a Geistlich Bio-Gide® membrane (Geistlich Pharma AG). Implants were inserted

three months after the augmentation procedure.

Implants were placed and restored according to the protocol as described in

detail in a previous clinical report (Den Hartog et al. 2009). Briefly, a surgical

template was used to install the implants at a depth of 3 mm apical to the buccal

and cervical aspect of the prospective clinical crown. All implants were installed

with a torque controller (OsseoCare, Nobel Biocare AB) adjusted to an insertion

torque of 45 Ncm. A manual torque controller (Nobel Biocare AB) was used to

realize proper implant depth if this torque value was reached before the implant

had reached its planned position.

In the immediate group, an implant-level impression was made. A healing

abutment was connected to the implants in the immediate group and a cover

screw to the implants in the conventional group. Before wound closure and if nec-

essary, in both study groups implant dehiscences or fenestrations were covered

with autogenous bone chips collected during implant bed preparation and anor-

ganic bovine bone (Geistlich Bio-Oss®) overlaid with Geistlich Bio-Gide®. Within

24 hours, a screw-retained provisional crown was placed in the immediate group.

This crown was free from centric and eccentric contacts with the antagonist teeth.

Patients were instructed to follow a soft diet and to avoid exerting force on the

provisional restoration.

Patients in the conventional group were wearing a removable partial prosthe-

sis that did not interfere with the wound. These implants were uncovered after

three months and restored with a provisional crown according to the same pro-

cedure as in the immediate group.

After a provisional phase of three months for the conventional group and six

months for the immediate group (to allow for six months post-implant placement

for both study groups), a definitive crown was made consisting of an individually

fabricated zirconia abutment (Procera, Nobel Biocare AB). Depending on the lo-

cation of the screw access hole, crowns were either screw-retained by fusing por-

celain directly to the abutment or cement-retained by means of a zirconia Procera

coping (Nobel Biocare AB). Cemented-retained crowns were cemented with glass

ionomer cement (Fuji Plus cement, GC Europe, Leuven, Belgium).

All surgical procedures were performed by a single experienced oral and maxil-

lofacial surgeon. The prosthetic procedure was accomplished by two experienced

prosthodontists, and all crowns were fabricated by one dental technician.

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Outcome measuresThe primary outcome measure of this study was marginal bone level change

proximal to the implant 18 months after implant placement as measured on ra-

diographs.

Secondary outcome measures were implant survival, change in peri-implant

mucosal level, aesthetic outcome, papilla volume, amount of plaque, bleeding

after probing, probing pocket depth and patient satisfaction. Both the implant

and adjacent teeth were analyzed. The operationalization of variables is described

below.

Radiographic and photographic assessmentsAfter implant placement (baseline, T

0), and after 6 (T

6m, after definitive crown pla-

cement) and 18 months (T18m

), standardized digital intra-oral radiographs were

taken with a long-cone paralleling technique. Standardized digital photographs

(camera: Fuji-film FinePix S3 Pro) were gathered before implant placement (Tpre

)

and at T6m

and T18m

. The radiographic and photographic procedure has been des-

cribed in detail by Meijndert et al. (Meijndert et al. 2004). For calibration of the

photographs, a calibrated probe was held in close contact and parallel to the long

axis of a tooth adjacent to the implant. All measurements were done by one and

the same examiner. The examiner was blinded for the photographs and the radio-

graphs taken at T6m

and T18m

. The radiographic examination could not be blinded

for the radiographs collected after implant placement (baseline, T0), since the

study group could be deduced from these radiographs. Full-screen analysis of the

radiographs was performed using specifically designed software. Radiographs

were calibrated according to the known diameter of the implant. Reference points

were marked and marginal bone levels proximal to the implant were measured ac-

cording to the first bone-to-implant contact together with marginal bone levels of

the adjacent teeth (Figure 1). Full-screen analysis of the photographs was perfor-

med using Adobe Photoshop (Adobe Photoshop CS3 Extended, Adobe Systems

Inc., San Jose, USA). After calibration, mid-facial mucosal and papilla levels of the

implant were measured after definitive crown placement (from T6m

). Mid-facial

gingival levels of the adjacent teeth were measured from Tpre

. The incisal edges of

the implant crown and adjacent teeth were used as reference.

To assess the reliability of the radiographic and photographic examination,

30 radiographs and photographs (15 from each study group) were randomly se-

lected and were measured by two examiners and by one examiner twice with a

two-week interval. The intra-observer agreement of the photographic examination

was tested earlier and reported as good with a mean difference of 0.11 ± 0.02 mm

between both times of measurements (Meijndert et al. 2004).

Clinical assessmentsAt T

pre (before implant placement), T

6m and T

18m patients were seen for clinical

data collection. Both the implant and the adjacent teeth were analyzed at the fa-

cial aspect. All data were retrieved by one and the same examiner. Variables were:

plaque, using the modified plaque index (Mombelli et al. 1987), bleeding, using the

modified sulcus bleeding index (Mombelli et al. 1987), volume of the interproximal

papilla, using the papilla index (Jemt 1997) and probing pocket depth, measured

to the nearest 1 mm using a manual periodontal probe (Williams Color-Coded

Probe, Hu-Friedy, Chicago, USA). During follow-up, implant survival was regis-, Hu-Friedy, Chicago, USA). During follow-up, implant survival was regis-

tered (defined as the existence of an implant in the oral cavity (Laney 2007).

Aesthetic assessmentsThe aesthetics of the peri-implant mucosa and implant crown were determined

on photographs taken at T18m

by using the Implant Crown Aesthetic Index (ICAI)

Figure 1. Schematic drawing of the radiographic assessment.

A and B, distances from reference line to marginal bone levels of implant and adjacent teeth. Abbreviations: ref=reference line.

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Reliability of radiographic and photographic assessmentsFor the intra-observer agreement of the radiographic examination, the mean dif-

ference between the observations was 0.03 ± 0.23 mm (limits of agreement:

-0.43 mm and 0.49 mm). For the inter-observer agreement, the mean difference

(Meijer et al. 2005) and the Pink Esthetic Score-White Esthetic Score (PES/WES)

(Belser et al. 2009). Measurements were done by one observer who was blinded

for the group allocation. The inter-observer reliability was assessed according to

10 randomly selected photographs from each study group (20 in total) that were

judged by two observers and by one observer with a two-week interval. The intra-

observer reliability has been reported as acceptable in earlier studies (Meijer et

al. 2005, Belser et al. 2009).

Patient satisfactionPatient satisfaction was assessed using a self-administered questionnaire to be

completed at T6m

and T18m

. The questionnaire comprised of questions or state-

ments that could be answered on a 5-point rating scale ranging from ‘very dis-

satisfied’ and ‘not in agreement’ (score 1) to ‘very satisfied’ and ‘in agreement’

(score 5). Topics were aesthetics, function and treatment procedure. Furthermore,

patients were asked to mark their overall satisfaction on a 10 cm Visual Analogue

Scale (VAS) having end phrases ‘very dissatisfied’ (0) on the left end and ‘very

satisfied’ (10) on the right end.

Data analysisA non-inferiority analysis was used to compare immediate loading with conven-

tional loading. Non-inferiority of immediate to conventional loading was defined

as less than 0.5 mm mean marginal bone loss (both proximal sides combined). It

was assumed that a mean marginal bone loss of 1.0 ± 0.6 mm would occur from

implant placement to 18 months thereafter for implants restored according to a

conventional protocol (Den Hartog et al. 2008). With a one-sided significance

level of 5% and a power of 90%, a minimum of 26 patients per group was re-

quired. The number of patients per group was set at 31 to deal with withdrawal.

The intra-and interobserver agreement for the radiographic and photographic

assessments were expressed as the 95% limits of agreement (Altman 1991), rep-

resenting the interval containing 95% of the differences between the observations

to be compared. In addition, intraclass correlation coefficients were calculated for

continuous variables and linear weighted kappa (κ) for categorical variables.

For between-group comparisons of numeric and normally distributed vari-

ables (assessed using Kolmogorov-Smirnov test), t-tests were used. Variables

that were not normally distributed were statistically explored with Mann-Whitney

tests. Friedman tests were applied for several within-group comparisons and Wil-

coxon signed-rank tests to compare two dependant conditions.

In all analyses, a significant level of 0.05 was chosen. Data were analysed us-

ing the Statistical Package for Social Sciences (version 16.0, SPSS Inc, Chicago,

IL, USA).

Table 1. Baseline characteristics and treatment specifications of 62 pa-tients treated with an immediate or conventional implant procedure.

VariableImmediate loading

(n=31)Conventional loading (n=31)

Mean age Range (years)

38.4 ± 14.0 18 - 66

40.1 ± 14.4 18 - 67

Male/female ratio 9 / 22 17/14

Tooth gap position I

1 / I

2 / C / P

114 / 10 / 4 / 3 18 / 8 / 3 / 2

Cause of tooth absence Fracture (crown or root) Agenesis Endodontic failure Periodontal failure Root resorption

2261-2

154822

Augmentation before implant surgery*

9 11

Implant diameter 3.5 mm 4.3 mm

1021

1021

Implant length 13 mm 16 mm

427

229

Implant-tooth distance Mean ± SD (mm) Range

2.16 ± 0.660.54 – 4.37

2.17 ± 0.770.45 – 5.26

Final restoration Screw-retained Cement-retained

1218

1219

*Implants were installed after three months.

Abbreviations: SD = standard deviation.

results

A total of 62 patients were allocated to the study groups of this trial (Table 1).

Most of the teeth that were lost had a history of trauma. All implants were placed

with a minimum insertion torque of 45 Ncm. Details about the surgical and pros-

thetic procedures are depicted in Table 1. There were no drop-outs and all pa-

tients attended the follow-up visits.

Tab

le 2

. (C

on

tin

ued

)

Bas

elin

e*T

6m

T18

m

Imm

.C

onv.

Imm

.C

onv.

Imm

.C

onv.

Pro

bin

g po

cket

dep

th (m

m)

M

esia

l of

impl

ant

D

ista

l of

impl

ant

M

id-f

acia

l of

impl

ant

P

roxi

mal

of

teet

h‡

M

id-f

acia

l of

teet

h

2.0

3 ±

0.4

41.

35 ±

0.3

72.

03

± 0

.51

1.37

± 0

.39

3.0

7 ±

0.9

13.

37 ±

0.9

32.

78 ±

0.5

81.

81 ±

0.4

51.

45 ±

0.7

0

3.0

3 ±

0.8

93.

50 ±

0.8

23.

07

± 0

.74

1.9

2 ±

0.4

91.

40 ±

0.4

2

3.28

± 1

.03

3.6

2 ±

1.12

3.14

± 0

.92

1.87

± 0

.56

1.55

± 0

.75

3.19

± 0

.91

3.81

± 1

.28

3.32

± 0

.79

1.9

9 ±

0.6

01.

37 ±

0.3

4

Plu

s-m

inu

s va

lues

are

mea

ns

± SD

. *

Aft

er im

plan

t pla

cem

ent f

or b

one

leve

ls a

nd

befo

re im

plan

t pla

cem

ent f

or g

ingi

val l

evel

s an

d po

cket

dep

ths.

# O

ne

impl

ant w

as lo

st th

ree

wee

ks a

fter

impl

ant p

lace

men

t. ‡ M

esia

l an

d di

stal

sid

es c

ombi

ned

.A

bbre

viat

ion

s: I

mm

=im

med

iate

load

ing,

Con

v=co

nve

nti

onal

load

ing,

T6

m=

6 m

onth

s af

ter

impl

ant p

lace

men

t, T

18m

= 18

mon

ths

afte

r im

plan

t

plac

emen

t.

Tab

le 2

. C

han

ges

in

mar

gin

al b

on

e le

vel

and

mar

gin

al s

oft

tis

sue

leve

l at

im

plan

t an

d t

oo

th s

ides

fro

m b

asel

ine

to 1

8 m

on

ths

Bas

elin

e* -T

6m

T6

m- T

18m

Bas

elin

e*- T

18m

Imm

. (n

=30

)#

Con

v.(n

=31)

Imm

.(n

=30

)#

Con

v.(n

=31)

Imm

.(n

=30

)#

Con

v.(n

=31)

Mar

gin

al b

one

leve

l ch

ange

s (m

m)

M

esia

l of

impl

ant

D

ista

l of

impl

ant

M

esia

l too

th s

ide

D

ista

l too

th s

ide

-0.7

3 ±

0.5

4-0

.75

± 0

.68

-0.2

0 ±

0.3

9-0

.26

± 0

.47

-0.7

9 ±

0.6

2-0

.81

± 0

.76

-0.2

5 ±

0.3

8-0

.18

± 0

.34

-0.1

3 ±

0.5

5-0

.19

± 0

.35

-0.0

2 ±

0.2

20

.02

± 0

.45

-0.1

3 ±

0.4

0-0

.09

± 0

.41

0.0

3 ±

0.2

8-0

.03

± 0

.42

-0.8

7 ±

0.5

5-0

.95

± 0

.84

-0.2

2 ±

0.3

8-0

.24

± 0

.40

-0.9

1 ±

0.6

6-0

.90

± 0

.77

-0.1

7 ±

0.4

0-0

.29

± 0

.50

Impl

ant b

one

loss

(%)‡

≤

1 m

m

1-2

mm

≥

2 m

m

71.6 25 3.3

62.

933

.93.

2

9

6.7

1.7

1.7

100 0 0

63.

3 30 6.7

56.5

38.7

4.8

Mar

gin

al s

oft t

issu

e le

vel c

han

ges

(mm

)

Mes

ial i

mpl

ant p

apill

a

Dis

tal i

mpl

ant p

apill

a

Mid

-fac

ial o

f im

plan

t

Mes

ial t

ooth

Dis

tal t

ooth

-0

.20

± 0

.38

-0.4

1 ±

0.5

2-0

.13

± 0

.39

-0.3

3 ±

0.5

1

0.4

1 ±

0.4

90

.27

± 0

.49

0.0

6 ±

0.4

2-0

.04

± 0

.23

0.1

0 ±

0.3

0

0.1

9 ±

0.2

90

.35

± 0

.52

-0.0

9 ±

0.3

4-0

.09

± 0

.25

0.0

0 ±

0.3

0-0

.25

± 0

.42

-0.3

2 ±

0.5

1-0

.22

± 0

.36

-0.3

3 ±

0.3

6

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92 93

for the radiographs and photographs was -0.02 ± 0.33 mm (limits of agreement:

-0.68 and 0.64 mm) and -0.02 ± 0.18 mm (limits of agreement: – 0.38 and 0.34

mm), respectively.

The intraclass correlation coefficients were 0.95 and 0.98 for the radiographic

inter- and intra-observer agreement, respectively, and 0.99 for the photographic

inter-observer agreement, all signifying high levels of agreement.

Marginal bone level changeThe mean marginal bone loss (mesial and distal implant sides combined) from

implant placement (baseline, T0) to 18 months thereafter (T

18m) was 0.91 ± 0.61

mm in the immediate group [95% confidence interval (CI): 0.69-1.13] and 0.90

± 0.57 mm in the conventional group [95% CI: 0.70-1.10] (P > 0.05)(Table 2).

In both study groups the amount of bone loss proximal to the implant had de-

creased significantly after the second follow-up visit (T6m

) (Table 2). There were no

significant differences between both study groups regarding bone level changes

at the adjacent teeth.

Clinical outcomeOne implant in the immediate group was lost three weeks after placement due

to high mobility. The implant survival rate at T18m

was 96.8 % for the immediate

group and 100% for the conventional group (P>0.05).

No between-group differences in soft tissue levels changes around the im-

plants and adjacent teeth were observed (Table 2). After definitive crown place-

ment, the level of the mid-facial peri-implant mucosa remained stable while a

mean gain of the papilla level of 0.34 ± 0.49 mm and 0.27 ± 0.42 mm was ob-

served in the immediate and conventional group, respectively (P>0.05) (Table

2). From Tpre

to T18m

, the mid-facial gingival level of the adjacent teeth showed a

mean recession of 0.29 ± 0.44 mm in the immediate group and 0.28 ± 0.36 mm

in the conventional group (P>0.05), which predominately occurred during the

first evaluation period.

The clinical assessments yielded no significant differences between both groups

for probing pocket depth (Table 2), plaque index, bleeding index and papillae index.

Bleeding index scores of the adjacent teeth were significantly lower compared to

the scores of the implants (Figure 2). The volume of the distal papillae, expressed

in papilla index scores, increased significantly during follow-up (Figure 3). Plaque

index scores were low at both follow-up visits. At T18m

, a plaque score of 1 was as-

signed to three implants in both study groups. All other implants did not show any

plaque. Within-group analysis revealed lower plaque scores for the adjacent teeth

at T6m

and T18m

compared to the preoperative situation (Tpre

)(P<0.05).

Figure 2. Frequency distribution of bleeding index scores for implants and adjacent teeth at 18 months after implant placement.

Abbreviations: Imm. = immediate loading, Conv. = conventional loading.

0%

20 %

40%

60%

80%

100%

score 3, heavy or profuse bleeding

score 2, confluent line of blood

score 1, isolated bleeding spots

score 0, no bleeding

Conv.Imm. Conv.Imm.

Teeth T18 Implant T18

Bleeding Index

71 74

22

48

31

48

7

19

1914

7

29

Figure 3. Frequency distribution of papilla index scores at 6 and 18 months after implant placement.

Abbreviations: Imm. = immediate loading, Conv. = conventional loading.

0%

20%

40%

60%

80%

100%

score 3, papilla fills up entire proximal space

score 2, at least half of the papilla

score 1, less than half of the papilla

score 0, no papilla

Conv.Imm.Conv.Imm.T6 T18

Papilla Index

28

22

52

34

45

22

18

47

28

43

35

19

Cha

pter

5

94

Aesthetic outcomeThe PES/WES showed satisfactory inter-observer agreement (weighted κ of 0.70

for the PES and 0.64 for the WES). However, the ICAI showed only satisfactory

inter-observer agreement for the assessment of the mucosa (κ-value 0.62 for the

mucosa and 0.41 for the crown). Therefore, the aesthetics of the implant crowns

were only evaluated using WES.

No differences were noticed regarding the aesthetics of the peri-implant mu-

cosa (pink aesthetics) and the implant crown (white aesthetics) as measured

with both aesthetic evaluation instruments (P>0.05). The pink aesthetics were

judged with a mean PES of 7.1±1.5 (range 3-10) and 6.5±1.63 (range 4-10) for the

immediate and conventional group, respectively. According to the ICAI, the pink

aesthetics were satisfactory in 24 cases (80%) in the immediate group and 19

cases in the conventional group (62%), of which 1 case in both groups showed ex-

cellent pink aesthetics. The white aesthetics in the immediate group were judged

with a mean WES of 7.8±1.5 (range 4-10) and in the conventional group with a

mean of 7.6±1.6 (range 4-10).

Patient satisfactionPatient satisfaction was high in both study groups and no differences were ob-

served between the groups (Table 3). At both follow-up visits (T6m

and T18m

) one-

third of the patients in the conventional group mentioned the healing time of the

implant as long.

dIscussIon

This randomized clinical trial revealed that the treatment outcome of immediate

loading of a single-tooth implant in the maxillary anterior zone is not less favora-

ble than conventional loading. After 18 months of follow-up, both treatment strat-

egies showed an equal amount of radiographic peri-implant marginal bone loss

and similar outcomes regarding survival, soft tissue aspects, aesthetic outcome

and patient satisfaction.

Studies on immediate loading are often founded on implant survival rates.

This is indeed a major outcome determining treatment success to a high extent.

In our study, survival rates were 96.8% for the immediate group (one implant

failed) and 100% for the conventional group. These high survival rates were con-

firmed by other studies on immediately loaded implants, even when inserted in

fresh extraction sockets (Den Hartog et al. 2008). We realize that the sample size

of our study was too small to demonstrate whether immediate loading was non-

inferior to conventional loading with respect to implant survival. Additional (long-

term) studies would be helpful to draw firm conclusions regarding the potential Tab

le 3

. P

atie

nt

sati

sfac

tio

n r

egar

din

g f

un

ctio

n, a

esth

etic

s, t

reat

men

t pr

oce

du

re a

nd

gen

eral

sat

isfa

ctio

n.

T6

m

% S

atis

fied

*

T18

m

% S

atis

fied

*

Imm

. (n

=30

)**

Con

v.(n

=31)

Imm

.(n

=30

)**

Con

v.(n

=31)

Fu

nct

ion

E

atin

g

Spe

akin

g

97

97

94

94

100

100

97

100

Aes

thet

ics

C

olou

r of

the

crow

n

For

m o

f th

e cr

own

C

olou

r of

the

mu

cosa

aro

un

d th

e cr

own

F

orm

of

the

mu

cosa

aro

un

d th

e cr

own

100

93

97

87

100

97

90

80

93

100

97

87

97

100

87 87

% I

n a

gree

men

t*%

In

agr

eem

ent*

Imm

.C

onv.

Imm

.C

onv.

Tre

atm

ent p

roce

dure

T

he

hea

ling

tim

e of

the

impl

ant w

as lo

ng

I

did

n’t

like

the

visi

ts to

the

den

tist

to m

ake

the

crow

n

I r

egre

t th

at I

ch

oose

this

trea

tmen

t

I w

ould

rec

omm

end

the

trea

tmen

t to

oth

er p

atie

nts

n.a

.0 0 97

26 3 0 100

n.a

.3 0 100

32 10 0 100

Gen

eral

sat

isfa

ctio

n

(V

AS-

scor

e; m

ean

±SD

)9

.2 ±

0.8

9.0

± 1

.09

.3 ±

0.9

8.9

± 1

.0

* R

epre

sen

ts p

erce

nt s

atis

fied

or

in a

gree

men

t on

5-p

oin

t sca

le (4

or

5 eq

ual

s sa

tisfi

ed o

r in

agr

eem

ent)

.

** O

ne

impl

ant w

as lo

st th

ree

wee

ks a

fter

pla

cem

ent.

Abb

revi

atio

ns:

Im

m=I

mm

edia

te lo

adin

g, C

onv=

Con

ven

tion

al lo

adin

g, T

6m

= 6

mon

ths

afte

r im

plan

t pla

cem

ent,

T18

m=

18 m

onth

s af

ter

impl

ant p

lace

men

t,

n.a

., n

ot a

pplic

able

, VA

S= v

isu

al a

nal

ogu

e sc

ale.

Cha

pter

5

Imm

edia

te lo

adin

g

5

96 97

time of the implant as long. Although, Levi et al. (2003) found that treatment time

was not a critical factor for overall satisfaction, the shorter treatment time of im-

mediate loading might serve these patients.

It is important to reach sufficient primary implant stability before performing

immediate loading. However, the threshold for sufficient primary stability has not

been adopted uniformly in studies on immediate single-tooth implant loading.

Furthermore, different methods were used to assess primary implant stability

or the method to assess stability was not reported (Den Hartog et al. 2008). We

utilized insertion torque as a diagnostic tool to express implant stability. Since it

has been reported that insertion torque is related to the amount of micromotion

(Trisi et al. 2009), we believe that this is a viable method. In our study, all im-

plants could be installed with a minimum insertion torque of 45 Ncm. Although

a lower value was not considered as an exclusion criterion beforehand, this may

introduce a higher risk of implant failure. A minimum torque value of 35 Ncm

has been successfully adopted in other studies on immediate loading, even when

inserted in fresh extraction sites (Wang et al. 2006, De Rouck et al. 2009).

In our study, provisional crowns were free from centric and eccentric contacts

with the antagonist teeth. This strategy has been defined as immediate non-func-

tional loading (Laney 2007) and loading occurs from lip and tongue pressure and

contact with food, but not from contact with the opposing dentition. Results from

single implant studies on immediate functional loading with a (provisional) crown

in centric occlusion, suggest that this might lead to comparable survival rates as

immediate non-functional loading (Rao & Benzi 2007, Glauser et al. 2007, Schin-

caglia et al. 2008). However, these studies focussed on tooth replacements in

posterior regions in particular where implants were subjected to more vertically

directed forces. In the anterior region, the lateral component of occlusal force is

more dominant and could act as a disrupting factor in the process of implant inte-

gration (Katona et al. 1993, Lin et al. 2007). We did not experience any problems to

create a non-occluding provisional crown with acceptable aesthetics and therefore

recommend this more reserved strategy above a functional loading concept. Fur-

thermore, a dominant role should be ascribed to carefully instructing the patient

to follow a soft diet and to avoid exerting force on the provisional restoration.

In conclusion, this study demonstrates that - on the short term - immediate

loading of a single-tooth implant in the maxillary aesthetic zone leads to a treat-

ment outcome that is not less favorable than conventional loading. As immediate

loading reduces the treatment time and could offer more comfort for the patient,

we recommend this strategy to be considered as an alternative to conventional

loading. However, the concept of immediate loading should be performed accord-

ing to a specified protocol with attention to adequate primary implant stability, a

non-occluding provisional crown and careful patient instruction.

hazardous effect of immediate loading on the process of osseointegration.

No differences were observed between immediate and conventional loading

regarding marginal bone loss at 6 and 18 months post-implant placement and

the values we found were consistent with what has been reported in other studies

on immediate and conventional single-tooth implants in the anterior zone (Hall

et al. 2007, Den Hartog et al. 2008, Degidi et al. 2009). Since it is known that the

proximal bone level next to the adjacent teeth is highly relevant for the level of the

proximal papillae of the implant (Choquet et al. 2001, Kan et al. 2003, Block et

al. 2009), also these bone levels were taken into consideration as an important

predictor for the aesthetic outcome. In both study groups, only a small amount

of bone loss at the adjacent teeth was noticed during follow-up. It is question-

able whether this amount of bone loss affected the level of the implant papillae,

which gained height during follow up. However, it should be realized that implant

therapy is not without consequences for the mid-facial level of the adjacent teeth,

showing a recession of about 0.3 mm in both groups with an even standard de-

viation.

There is growing evidence that immediate loading of implants inserted in fresh

extraction sockets would lead to more favorable soft tissue levels compared to a

delayed strategy (De Rouck et al. 2009, Block et al. 2009). These studies showed

that immediate stabilization of the soft tissue after tooth removal by means of im-mmediate stabilization of the soft tissue after tooth removal by means of im-

mediate implant placement and immediate placement of the provisional crown,

revealed 0.75 to 1 mm more soft tissue preservation mid-facially. However, the re-

liability of this strategy should be established by more well-designed studies (Den

Hartog et al. 2008). In our study, all implants were inserted in healed sites. After

tooth removal, the walls of the alveolus undergo substantial resorption affecting

the soft tissue anatomy (Schropp et al. 2003, Araujo & Lindhe 2005). It could be

that for healed sites, the potential positive effect of an immediate (provisional)

crown on soft tissue preservation subsided. When using the PES and ICAI as

instruments to express soft tissue aesthetics, at least no significant difference

between immediate and conventionally loaded implants was observed. The same

applied to the volume of the papilla assessed with the papilla index. This index in

particular could, however, be more related to the bone level of the adjacent teeth

as discussed earlier. More clinical trials are needed investigating the influence of

an immediately placed (provisional) crown on soft tissue parameters.

Overall patient satisfaction was high in both study groups and patients were

satisfied regarding function, aesthetics and treatment procedure. Other studies

on anterior single-tooth implants reported comparable overall satisfaction scores

of 8.8 and higher (also using VAS) (Schropp et al. 2004, Den Hartog et al. 2008).

As confirmed by other studies (Levi et al. 2003, Schropp et al. 2004), a substan-

tial percentage of conventionally treated patients (30%) experienced the healing

Cha

pter

5

Imm

edia

te lo

adin

g

5

98 99

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This is an edited version of the manuscript: Den Hartog, L., Raghoebar, G.M., Stellingsma, K.,

Meijer, H.J. Immediate loading and customized restoration of a single implant in the maxillary

esthetic zone: a clinical report. Journal of Prosthetic Dentistry 2009; 102: 211-215

6.

Immediate loading and customized restoration

of a single-tooth implant in the maxillary aesthetic

zone: a clinical report

Cha

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rep

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102 103

AbstrAct

The replacement of a single missing anterior tooth with a dental implant is

a demanding therapy. This report describes a treatment in which an ante-

rior maxillary implant was immediately restored with a provisional restora-

tion. During the provisional phase, an optimal emergence profile was cre-

ated by adjusting the provisional restoration. An impression was made with

an individually fabricated impression post for an accurate reproduction of

the established emergence profile and finally a screw-retained all-ceramic

crown was placed. By implementing this protocol, an optimal definitive re-

sult could be achieved together with immediate patient satisfaction. How-

ever, cooperation between several disciplines and careful patient selection

were required.

IntroductIon

The application of dental implant to restore a missing tooth in the anterior den-

tition is challenging. In the aesthetic zone, both the appearance of the implant

crown and the soft tissue contribute to a successful treatment outcome and

should consequently be in harmony with the surrounding dentition (Chang et al.

1999, Belser et al. 2004). To accomplish the desired result, meticulous pre-op-

erative treatment planning is crucial together with cooperation between several

disciplines during the restorative phase.

In recent literature, several treatment strategies using dental implants have

been reported to replace a missing tooth (Den Hartog et al. 2008). Among these,

interest has been attributed to immediate or early loading protocols in which a

provisional restoration is placed soon after implant placement. Clinical studies of

immediate or early loading have reported favorable treatment outcomes in terms

of implant survival, marginal bone resorption, soft tissue level and the incidence

of complications for treatment in which implants were inserted in healed sites

(Ericsson et al. 2000, Andersen et al. 2002, Cooper et al. 2007, Hall et al. 2007) as

well as implants placed in fresh extraction sockets (Crespi et al. 2008, de Rouck et

al. 2008). However, a recent systematic review (Den Hartog et al. 2008) showed

that well-designed controlled studies that compare these approaches with con-

ventional protocols are scarce and whether or not superior aesthetic outcomes

could be achieved remained inconclusive. Immediate or early implant loading

provides several advantages for the patient including a shorter overall treatment

time, avoidance of a second-stage operation and eliminating the need for a re-

movable prosthesis during the healing phase. However, these protocols require

careful pre-operative planning and patient selection. Furthermore, good primary

implant stability is a prerequisite (Esposito et al. 2007), in addition to the develop-

ment of a protected occlusion to create a non-occluding provisional crown.

Another important development has been the introduction of alumina- and

zirconia-based ceramic abutments made with computer-aided design/compu-

ter-aided manufacturing (CAD/CAM) technology. Ceramic abutments are high-

strength (Sundh & Sjögren 2008, Yüzügüllü & Avci 2008,) biocompatible (We-

lander et al. 2008) and have allowed new options to improve the natural appear-

ance of the implant crown. However, little is known about the long-term clinical

performance of these abutments (Linkevicius & Apse 2008).

The purpose of this clinical report was to demonstrate an immediate implant

loading protocol for restoration of a missing central incisor. After the provisional

restoration phase, an individually fabricated impression post was used and sub-

sequently a definitive screw-retained one piece all-ceramic crown was placed.

Cha

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104 105

Clinical reportA 47-year-old woman consulted the Department of Oral and Maxillofacial Surgery

(University Medical Center Groningen, University of Groningen, Groningen, the

Netherlands) with a missing right central incisor (Figure 1) lost due to a trau-

matic injury. At the time of the consultation she was wearing a removable partial

denture and desired a durable and fixed restoration, without involvement of the

adjacent teeth. The patient was healthy, did not smoke and intraoral examination

revealed a healthy well-maintained dentition. Clinically, adequate bone volume

was present at the future implant site. In all dimensions, sufficient space was

available for an implant crown with an anatomical design. Radiographically, no

pathology of the bone and adjacent teeth was noted. Because of the favorable

starting point, it was decided to use an immediate loading protocol.

Preoperatively, diagnostic casts were made with a diagnostic arrangement

representing the future implant crown in an ideal position. Next, a transparent

acrylic resin template (Vertex Castapress; Vertex Dental, Zeist, the Netherlands)

was fabricated and a guide channel was prepared in the template to aid in proper

implant placement. Care was taken with the surgical guide so that the guidance

channel would direct the implant sufficiently toward the palate to accommodate

a screw-retained restoration.

One day before surgery, the patient started taking antibiotics (amoxicillin 500

mg, 3 times daily for seven days) and used a 0.2% chlorhexidine mouthwash

(Corsodyl; GlaxoSmithKline, Utrecht, the Netherlands) for oral disinfection. Fol-

lowing local anaesthesia (Ultracaine D-S Forte; Aventis Pharma, Hoevelaken, the

Netherlands) a slightly palatal crest-incision was made with extensions through

the buccal and palatal sulcus of the adjacent teeth. A minimal mucoperiosteal

flap was elevated to expose only the ridge crest (Figure 2). Then, an implant (No-

belReplace Tapered RP 16 mm, Nobel Biocare, Gothenburg, Sweden) was placed

according to the procedure prescribed by the manufacturer guided by the surgical

template. The shoulder of the implant was placed at a depth of 3 mm apical to the

buccal and cervical aspect of the prospective clinical crown to provide soft tissue

to develop an adequate emergence profile. Good primary implant stability was

obtained (> 45 Ncm, determined with Osseocare; Nobel Biocare). Next, an open-

tray impression was made at the implant level using a custom resin impression

tray (Lightplast base plates; Dreve Dentamid, Unna, Germany) and a polyether

impression material (Impregum Penta; 3M ESPE, St. Paul, Minnesota, USA.).

Finally, a healing abutment (NobelReplace; Nobel Biocare) was placed and the

wound was closed with sutures (Ethilon 5-0; Johnson & Johnson Gateway, Pis-

cataway, New Jersey, USA).

In the dental laboratory, a screw-retained provisional restoration was fabricated

consisting of an engaging temporary abutment (Temporary Abutment Engaging

Figure 1. Pre-operative view.

Figure 2. Exposure of the alveolar bone.

Figure 3. Screw-retained provisional crown placed same day after implant surgery.

Cha

pter

6

Clin

ical

rep

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6

106 107

Figure 5. Assembly of provisional crown with implant analog and impres-sion of cervical portion of provisional crown.

Figure 4. View of peri-implant soft tissue after the provisional restoration phase. Note established emergence profile.

NobelReplace; Nobel Biocare) against which composite resin (Solidex; Shofu Inc,

Kyoto, Japan) was modelled. Eight hours post-implant placement, the abutment

was removed and the provisional crown was placed and subsequently torqued to

32 Ncm (Figure 3). Special care was taken to prevent any centric and eccentric

occlusal contacts with the antagonist teeth. Furthermore, the provisional restora-

tion was contoured so that the peri-implant soft tissue was optimally supported.

In particular, the interproximal papillae were given enough space to regenerate.

The patient was instructed to follow a soft diet, to avoid exerting force on the pro-

visional restoration and to continue chlorhexidine rinses (Corsodyl; GlaxoSmith-

Kline, Utrecht, The Netherlands) for seven days. For pain control, ibuprofen 600

mg (Brufen Bruis 600; Abott B.V., Hoofddorp, The Netherlands, three times daily

for time needed) was prescribed and at two weeks post surgery the sutures were

removed.

The patient returned to the prosthodontist once a month for three months for

examination of the implant. During these sessions, implant mobility, oral hygiene

and occlusion were evaluated. Also, an important objective was the creation of an

ideal emergence profile by removing the provisional crown. Extraorally and where

needed, composite resin was removed or added to aspects of the crown to create

more space or more support for the soft tissue. In this process, special attention

was given to the shape of the proximal contour to provide an optimal condition

for the papillae to reach maturity.

Three months later (six months post-implant placement) an implant level im-

pression was made using an impression post (Impression Coping Implant Level

Open Tray NobelReplace; Nobel Biocare) that was customized in a way that the

obtained emergence profile could be transferred to the definitive restoration (Fig-

ure 4). To realize this, the provisional crown was assembled with an implant ana-

log (Implant Replica NobelReplace; Nobel Biocare) embedded in type IV dental

stone (GC Fuji Rock EP; GC Europe N.V., Leuven, Belgium). An addition silicone

impression (Futar D; Kettenbach GmbH & Co KG, Eschenburg, Germany) of the

cervical portion of the crown was made (Figure 5). Next, the latter was substituted

for an impression post and bis acrylic composite resin (Protemp; 3M ESPE, St.

Paul, Minn) was added to the post. After polishing the individualized post (Figure

6) it was inserted into the implant and an open-tray impression was made with a

polyether impression material (Impregum Penta; 3M ESPE) and a custom resin

impression tray (Lightplast base plates; Dreve Dentamid).

In the dental laboratory, a soft tissue cast was prepared. First, a waxing of

the definitive crown was made on a temporary abutment (Temporary Abutment

Engaging NobelReplace; Nobel Biocare). The screw access hole was located suf-

ficiently to the palate to create a screw-retained crown and to prepare an appropri-

ate abutment. Therefore, the waxing was cut back to the desired form and scanned

Figure 6. Customized impression post.

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Figures 7 & 8. Application of porcelain to individually fabricated Procera zirconia abutment to create a one-piece screw-retained definitive crown.

Figure 9. Clinical view of definitive implant crown 18 months after im-plant placement.

for fabrication of an individual zirconia abutment (Procera; Nobel Biocare AB).

Porcelain was added directly to the abutment to create a screw-retained one piece

definitive restoration (Figures 7 & 8). The restoration was placed and the abut-

ment screw was torqued with 32 Ncm. Finally, the screw hole was filled with a

cotton pellet and composite resin (Clearfil AP-X; Kuraray Medical Inc, Okayama,

Japan). The restoration has been in service for 18 months without complication

(Figure 9).

dIscussIon

This report describes an immediate loading protocol finalized with the placement

of a screw-retained all-ceramic restoration. A major prerequisite for immediate

loading is a high degree of primary stability in terms of high insertion torque

(Esposito et al. 2007). In this treatment, an initial insertion torque of at least 45

Ncm was reached. Although clinical studies on immediate single-tooth implant

loading reported varying minimal insertion torques for immediate loading, the

authors of this report adopted a threshold of 45 Ncm.

In this patient, a substantial maturation of the papillae occurred during the

provisional phase. Care was taken to ensure that the provisional crown did not

disturb this process, but served as a natural guide. Regeneration of papillae with

time has been reported in several studies (Jemt & Lekholm 2005, Schropp et

al. 2005), but the mechanism behind this phenomenon could not validly be ex-

plained. Some authors believed that this increase might be attributed to remod-

elling potential of the soft tissue to establish a proper biological height after the

surgical manipulation (Chang et al. 1999). It is widely accepted however, that the

interproximal bone level next to the adjacent teeth is important for the future level

of the interproximal papillae of the implant (Belser et al. 2004).

Finally, a screw-retained definitive restoration was fabricated. The advantages

of this type of restoration compared to a cement-retained restoration include

retrievability and no risks for cement remnants thereby excluding possible irrita-

tion of the peri-implant tissues. However, the presence of a screw access opening

decreases fracture resistance of the porcelain (Torrado et al. 2004). Furthermore,

screw-retained restorations necessitate precise implant positioning for a proper

palatal position of the screw access hole that does not interfere with the aesthet-

ics.

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References

Andersen, E., Haanaes, H.R. & Knutsen, B.M. (2002) Im-

mediate loading of single-tooth ITI implants in the anterior

maxilla: a prospective 5-year pilot study. Clinical Oral





International Journal of Oral and Maxillofacial Implants 19

Suppl, 30-42.





Cooper, L.F., Ellner, S., Moriarty, J., Felton, D.A., Paquette

D. & Molina, A. (2007) Three-year evaluation of single-tooth

implants restored 3 weeks after 1-stage surgery. International


Crespi, R., Capparé, P., Gherlone, E. & Romanos, G.E.

(2008) Immediate versus delayed loading of dental implants

placed in fresh extraction sockets in the maxillary esthetic

zone: a clinical comparative study. International Journal of

Oral and Maxillofacial Implants 23, 753-758.

De Rouck, T., Collys, K. & Cosyn, J. (2008) Immediate

single-tooth implants in the anterior maxilla: a 1-year case

cohort study on hard and soft tissue response. Journal of

Clinical Periodontology 35, 649-657.







Esposito, M., Grusovin, M.G., Willings, M., Coulthard, P.

& Worthington, H.V. (2007) Interventions for replacing

missing teeth: different times for loading dental implants.

Cochrane Database of Systematic Reviews 18, CD003878.

Ericsson, I., Nilson, H., Lindh, T., Nilner, K. & Randow, K

(2000). Immediate functional loading of Branemark single

tooth implants. An 18 months’ clinical pilot follow-up study.






Research 9, 34-45.

Jemt, T. & Lekholm, U. (2005) Single implants and buccal

bone grafts in the anterior maxilla: measurements of buccal

crestal contours in a 6-year prospective clinical study. Clini-

cal Implant Dentistry and Related Research 7, 127-135.

Kan, J.Y., Rungcharassaeng, K. & Lozada, J. (2003) Immedi-

ate placement and provisionalization of maxillary anterior

single implants: 1-year prospective study. International


Linkevicius, T. & Apse P. (2008) Influence of abutment

material on stability of peri-implant tissues: a systematic re-

view. International Journal of Oral and Maxillofacial Implants

23, 449-456

Meijndert, L., Raghoebar, G.M., Meijer H.J. & Vissink, A.




Research 19, 1295-1303.




Palattella, P., Torsello, F. & Cordaro, L. (2008) Two-year

prospective clinical comparison of immediate replacement

vs. immediate restoration of single tooth in the esthetic

zone. Clinical Oral Implants Research 19, 1148-1153.




trial. International Journal of Oral and Maxillofacial Implants

20, 753-761.

Sundh, A. & Sjögren G. (2008) A study of the bending

resistance of implant-supported reinforced alumina and

machined zirconia abutments and copies. Dental Materials

24, 611-617.

Torrado, E., Ercoli, C., Al Mardini, M., Graser, G.N., Tal-

lents, R.H. & Cordaro L. (2004) A comparison of the

porcelain fracture resistance of screw-retained and cement-

retained implant-supported metal-ceramic crowns. Journal of

Prosthetic Dentistry 91, 532-537.

Welander, M., Abrahamsson, I. & Berglundh T. (2008) The

mucosal barrier at implant abutments of different materials.


Yüzügüllü, B. & Avci, M. (2008) The implant-abutment in-

terface of alumina and zirconia abutments. Clinical Implant

Dentistry and Related Research 10, 113-121.

This is an edited version of the manuscript: Trauma to an implant-supported crown that was saved

by the fixation screw: a case report. Den Hartog, L., Meijer, H.J.A., Stellingsma, K., Santing, H.J.,

Raghoebar, G.M. Dental Traumatology 2010; 26: 366-369

7.

Trauma to an implant crown that was saved by the

fixation screw: a case report

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AbstrAct

A traumatic impact to an implant crown might damage the implant, crown

and peri-implant tissue. Ideally, only a small prosthetic retreatment is need-

ed for restoration, since a complicated prosthetic retreatment or a surgical

retreatment in particular, could be very inconvenient for the patient. How-

ever, there is a deficiency in literature on how the implant, restoration and

surrounding tissues generally react to impact forces. This report demon-

strates a case of trauma to an implant crown in the maxillary anterior zone

resulting in a palatal displacement of the crown. After careful examination

and follow-up, it appeared that only the fixation screw was damaged, while

the implant, crown and peri-implant tissue remained unharmed. Thanks to

the protective qualities of the implant system, an easy prosthetic retreat-

ment could restore the implant crown and a surgical retreatment was pre-

vented.

IntroductIon

It is known that a missing anterior tooth can be successfully replaced with a den-

tal implant (Creuger et al. 2000, Belser et al. 2004, Den Hartog et al. 2008).

However, after implant therapy is completed, several complications might oc-

cur ( Berglundh et al. 2002, Jung et al. 2008). These vary from peri-implant soft

tissue lesions (viz. peri-implant mucositis, soft tissue dehiscence, fistula) and

abnormal marginal peri-implant bone loss (peri-implantitis), to more technical-

related complications as implant fracture and fracture or loosening of the abut-

ment, fixation screw or crown. Overload by occlusal forces is one of the factors

that may induce these complications (Esposito et al. 1999, Piatelli et al. 2003,

Khraisat et al. 2004). Besides this overload, a relatively rare factor is an acute ex-

cessive load caused by a dental trauma. There is a deficiency in literature concern-

ing the consequences of these suddenly high forces to the implant, restoration

and surrounding tissues. To date, only three case reports have been published

that present the consequences of a trauma to implant crowns (Flanagan 2003,

Stuebinger et al. 2004, Allen & Allen 2006). In two cases, the trauma resulted in

damaged implant crowns and a bent fixation screw, but the implants sustained

no damage (Flanagan 2003, Stuebinger et al. 2004). In one case however, the

implant gave way resulting in a palatal movement of the implant within the bone,

possibly in combination with a fracture of the alveolar process (Allen & Allen

2006). Because the implant remained osseointegrated, it was restored with a

new implant crown.

This report is aimed to further demonstrate the consequences of a trauma to

an anterior implant crown and the subsequent therapeutic approach that was

performed.

Case reportAn 18-year-old man was referred to the Department of Oral and Maxillofacial Sur-

gery (University Medical Center Groningen, University of Groningen, Groningen,

the Netherlands) for replacement of a right central incisor with an implant sup-

ported crown. Six years ago this tooth had been avulsed in a bicycle accident and

was subsequently replanted. Because of severe root resorption and a persistent

fistula, the tooth could not longer be saved. After extraction, an augmentation

procedure was performed with an autogenous retromolar bone graft, Geistlich

Bio-Oss® (Geistlich Pharma AG, Wolhusen, Switzerland) and Geistlich Bio-Gide®

(Geistlich Pharma AG) to reconstruct the alveolar process. Four months there-

after, a 16 mm Replace Select Tapered implant (Nobel Biocare AB, Göteborg,

Sweden) was placed according to a two-staged procedure. After the osseointegra-

tion period, the implant was restored with a one-piece screw-retained all-ceramic

crown (Procera, Nobel Biocare AB).

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Figure 2. Radiographic view after completion of implant therapy, before trauma.

Figure 3. Radiographic view after trauma. Note the small triangular gap at the distal implant-abutment interface.

Seven months later (14 months after implant placement), the patient con-

sulted our department following an accident 2 days previously in a swimming

pool in which his knee stroke his anterior dentition. He had no pain and only

complained about a disrupted occlusion because of displacement of the implant

crown. There were no extra-oral injuries. An intra-oral inspection showed that the

implant crown was displaced to the palatal, causing a premature contact (Figure

1). The implant crown was neither mobile nor damaged. A slight swelling and

redness of the facial peri-implant mucosa was noted. The adjacent natural teeth

were intact, vital and did not show increased mobility.

Figure 1. Implant supported crown, region 11; palatally displaced after trauma.

For radiographic examination, a maxillary anterior occlusal radiograph was

taken together with a peri-apical radiograph. No abnormalities were detected on

the occlusal radiograph. The peri-apical radiograph was closely compared with a

peri-apical radiograph that was taken before the accident, just after placement of

the crown. Distally, the implant-abutment interface showed a small triangular gap

(Figures 2 and 3). It was suggested that the displacement of the implant crown

was caused by deformation of the fixation screw. However, it was not certain that,

besides this, the alveolar process surrounding the implant had been fractured,

causing a displacement of the implant itself. Since the aesthetics were still ac-

ceptable for the patient, an expectative policy was pursued. It was possible to

leave the implant crown free from occlusion contacts by grinding the porcelain

of the palatal aspect of the implant crown. The patient was instructed to follow a

soft diet and to avoid force on the implant crown as much as possible. Follow-up

visits one and three months later showed status quo. On the last visit, the one-

piece screw-retained implant crown was removed. A torque wrench was necessary to

loosen the fixation screw that was clearly bent (Figure 4). A careful visual inspection

of the implant platform and implant crown revealed that both were undamaged. For

further investigation of the implant crown, it was installed on the original soft tissue

cast with the aid of a laboratory fixation screw. It was found that there was a good

fit with the implant analog and that the implant crown was properly located in har-

mony with the adjacent dentition (Figure 5). The palatal aspect of the implant crown

that was grinded earlier was restored in the dental laboratory by fusing a new layer

of porcelain. The implant crown was replaced on the implant and fixed with a new

fixation screw. The implant-abutment interface was approved radiographically and

finally the fixation screw was torqued. The screw hole was filled with a cotton pellet

and composite resin (Figure 6).

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dIscussIon

This report describes a case of trauma to an anterior implant crown. It appeared

that only the fixation screw had sustained damage. Apparently, a major part of the

impact energy was absorbed by the deflection of the fixation screw, thereby sav-

ing the crown, implant and alveolar bone. Thanks to this protective mechanism,

only a small prosthetic retreatment could restore the implant crown. More com-

plicated prosthetic retreatments or surgical retreatments in particular should be

prevented as much as possible. We believe that implant components could play

an important role in preventing serious damage to the implant or surrounding

tissue following an impact force.

With respect to the peri-implant bone, it is known that although bone is able to

absorb energy, a large force impact applied to an integrated implant, might lead

to microcracking or fracture of bone (Flanagan 2003). It is conceivable that as a

result, displacement of the implant occurs, or even worse, an extensive fracture

of the alveolar process. A study on the impact fracture resistance of implants and

abutments showed that 18 out of 20 implants that were embedded in a bone-

simulating material, remained intact and were displaced from the embedding

material with fracture of the embedding material as a consequence (Silva et al.

2009). In only two specimens with zirconia abutments, the abutments fractured.

Assumed that the bone-simulating material is representative of alveolar bone

structure, it was suggested that a facial trauma to an osseointegrated implant is

likely to lead to fracture of the alveolar bone, leaving the implant intact. To what

extent this would actually occur in the clinical situation, is not known. Only one

report describes a displacement of an implant after trauma, probably in combina-

tion with fracture of the labial cortical bone (Allen & Allen 2006). In this report

however, the traumatic incident was only four months after implant placement

and the authors hypothesized that the peri-implant bone was not yet maturated

and hardly organized, offering little resistance to force. Furthermore, it was ar-

gued that the low bone volume present at the implant region could be responsi-

ble for the implant displacement and possible fracture.

In our case, the trauma occurred 14 months after implant placement and even

though a pre-implant augmentation procedure was performed, the peri-implant

bone resisted. It turned out that only the fixation screw was damaged. However,

at the first consultation after trauma, we were not really sure if the bone sur-

rounding the implant had not been fractured, also causing a displacement of

the implant itself. Since the aesthetics were still acceptable for the patient and it

was possible to leave the implant crown free from occlusal forces, we decided to

adopt an expectative policy allowing the peri-implant bone to rest.

Little is known about how the implant and superstructure generally react to

an impact. If the superstructure has been damaged, this can be solved by re-

Figure 4. Bent fixation screw.

Figure 5. one-piece screw-retained all-ceramic crown replaced on the origi-nal soft tissue cast. The crown is in harmony with the adjacent dentition.

Figure 6. Clinical view after replacement of the crown with a new fixation screw.

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pairing or replacing the relevant component, on the condition that it is possible

to remove this component from the implant. However, if the implant has to be

replaced due to damage or a non-removable component, a complex surgical re-

treatment is needed with much inconvenience for the patient. In the study by

Silva et al. (2009), also impact tests were performed on implants clamped in

brass. They found that for implants with titanium abutments, an impact leads to

fracture of the abutment screw leaving the abutment and implant intact. Zirconia

abutments however, fractured in pieces, but no damage of the implant and abut-

ment screw was observed. It should be noted that in this study, implants with an

external implant-abutment connection were tested. Implant systems with inter-

nal abutment connections might react differently to an impact, but to our best

knowledge, impact tests on these connections are lacking in literature. On the

other hand, several studies investigated the strength of different implant-abut-

ment connections under compressive loading tests. These studies could provide

valuable information about the stability of implants under high forces. It was

found that abutments and abutment screws fractured or bent, while most of the

implants remained intact or showed only little damage (Boggan et al. 1999, Nor-

ton et al. 2000, Strub et al. 2003, Khraisat 2005, Steinebrunner et al. 2008). This

implies that under high forces, the implant is not the weakest link and in general

may remain standing after an impact. However, a comment should be made on

implants with a smaller diameter. Finite element stress models in which implants

with an internal connection were subjected to compressive loading showed that

especially implants with a narrow diameter (3.3 mm) are at risk to fracture, since

high stresses concentrated at the implant collar (Akça et al. 2003, Nagasawa et

al. 2008). Implants with a regular diameter (≥ 4 mm) showed a more favora-

ble stress distribution with lower stresses at the implant collar (Nagasawa et al.

2008). In our case, the patient was restored with a Replace Select Tapered implant

and a NobelProcera zirconia abutment. Att and coworkers (2006) evaluated the

fracture strength of implant-supported all-ceramic restorations under compres-

sive loading, for the same abutment and implant system as in our case. After

the load-to-fracture tests, no implant collar distortion was found for all of the

specimens.

It was of advantage that our patient was restored with a one-piece screw-re-

tained crown, since it was easy to remove and could be used again. Cement-re-

tained implant crowns are hard to remove without sacrificing crown material. Fur-

thermore, it proved to be helpful that we had documented the implant treatment

completely, including the radiographic documentation at various stages and that

we kept the original soft tissue cast on which the final crown was fabricated.

Although the incidence of trauma to implant restorations is not high, the

patient deserves a careful approach that is well-thought. The same is true for

preventing irreversible damage leading to complicated prosthetic or surgical re-

treatments. To our opinion the superstructure should be the weakest link if an

implant restoration is subjected to a traumatic impact, thereby preserving the

implant and surrounding tissue. Most ideally, the fixation screw absorbs most of

the energy thereby protecting the crown, abutment and implant. Moreover, it is

important that damaged implant components can be removed from the implant,

so that a prosthetic retreatment is feasible. Therefore, more research would be

helpful to explore the consequences of an impact to implant systems and corre-

sponding implant components.

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References

Akça, K., Cehreli, M.C. & Iplikçioğlu, H. (2003) Evaluation

of the mechanical characteristics of the implant-abutment

complex of a reduced-diameter morse-taper implant. A non-

linear finite element stress analysis. Clinical Oral Implant

Research 14, 444-454.

Allen, E.M. & Allen, P.F. (2006) Trauma to an osseointe-

grated anterior dental implant: a case report. Dental Trauma-

tology 22, 44-47.

Att, W., Kurun, S., Gerds, T. & Strub, J.R. (2006) Fracture

resistance of single-tooth implant-supported all-ceramic

restorations after exposure to the artificial mouth. Journal of

Oral Rehabilitation 33, 380-386.

Belser, U.C., Schmid, B., Higginbottom, F. & Buser D.



International Journal of Oral and Maxillofacial Implants 19,

Suppl 30-42.

Berglundh, T., Persson, L. & Klinge, B. A. (2002) Systematic

review of the incidence of biological and technical complica-

tions in implant dentistry reported in prospective longitudi-

nal studies of at least 5 years. Journal of Clinical Periodontol-

ogy 29, Suppl 3 197-212.

Boggan, R.S., Strong, J.T., Misch, C.E. & Bidez, M.W.

(1999) Influence of hex geometry and prosthetic table width

on static and fatigue strength of dental implants. Journal of

Prosthetic Dentistry 82, 436-440.

Creugers, N.H., Kreulen, C.M., Snoek, P.A.& De Kanter RJ.

(2000) A systematic review of single-tooth restorations sup-A systematic review of single-tooth restorations sup-

ported by implants. Journal of Dentistry 28, 209-217.

Den Hartog, L., Slater, J.J., Vissink, A., Meijer, H.J.&






Esposito, M., Hirsch, J., Lekholm, U. & Thomsen, P. (1999)

Differential diagnosis and treatment strategies for biologic

complications and failing oral implants: a review of the

literature. International Journal of Oral and Maxillofacial

Implants 14, 473-490.

Flanagan, D. (2003) External and occlusal trauma to dental

implants and a case report. Dental Traumatology 19, 160-164.

Jung, R.E., Pjetursson, B.E., Glauser, R., Zembic, A.,

Zwahlen, M. & Lang, N.P. (2008) A systematic review of the

5-year survival and complication rates of implant-supported

single crowns. Clinical Oral Implant Research 19, 119-130.

Khraisat, A., Abu-Hammad, O., Al-Kayed, A.M. & Dar-

Odeh, N. (2004) Stability of the implant/abutment joint in

a single-tooth external-hexagon implant system: clinical and

mechanical review. Clinical Implant Dentistry and Related


Khraisat, A. (2005) Stability of implant-abutment interface

with a hexagon-mediated butt joint: failure mode and bend-

ing resistance. Clinical Implant Dentistry and Related Research

7, 221-228.

Nagasawa, S., Hayano, K., Niino, T., Yamakura, K., Yoshida,

T., Mizoguchi, T. & et al. (2008) Nonlinear stress analysis

of titanium implants by finite element method. Journal of

Dental Materials 27, 633-639.

Norton, M.R. (2000) In vitro evaluation of the strength of

the conical implant-to-abutment joint in two commercially

available implant systems. Journal of Prosthetic Dentistry 83,

567-571.

Piattelli, A., Scarano, A., Favero, L., Iezzi, G., Petrone, G. &

Favero, G.A. (2003) Clinical and histologic aspects of dental

implants removed due to mobility. Journal of Periodontology

74, 385-390.

Silva, N.R., Nourian, P., Coelho, P.G., Rekow, E.D. &

Thompson, VP. (2009) Impact Fracture Resistance of two

Titanium-Abutment Systems Versus a Single-Piece Ceramic

Implant. Clinical Implant Dentistry and Related Research 3,

[Epub ahead of print].

Steinebrunner, L., Wolfart, S., Ludwig, K. & Kern M. (2008)

Implant-abutment interface design affects fatigue and

fracture strength of implants. Clinical Oral Implant Research

19, 1276-1284.

Strub, J.R. & Gerds, T. (2003) Fracture strength and failure

mode of five different single-tooth implant-abutment combi-

nations. International Journal of Prosthodontics 16, 167-171.

Stuebinger, S., Hodel, Y. & Filippi, A. (2004) Trauma to

anterior implants. Dental Traumatology 20, 169-171.

8.

General discussion

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The application of a dental implant to replace an anterior tooth is challenging.

One should not only strive to rehabilitate function, but also to restore the aesthet-

ics represented by the appearance of the implant crown and the peri-implant mu-

cosa. Besides, as holds for all implant cases, the tissue surrounding the implant

should remain healthy and stable over time for good long-term prognosis.

From the broad spectrum of materials and techniques available in aesthetic

implant dentistry, this thesis inquired into two aspects, namely the design of

the implant neck and the concept of immediate implant loading. Radiographic,

clinical and aesthetic outcome measures together with patient satisfaction were

assessed reflecting the quality of the final outcome. In this chapter the main re-

search outcomes are discussed. In the last paragraphs, clinical implications and

suggestions for future research are given.

Evidence from literature on single-tooth implants

in the aesthetic zone

A systematic review of the literature was performed to gain insight into the avail-

able evidence on the efficacy of using an implant to replace a missing anterior tooth

(Chapter 2). In this review, we focussed on single implants neighboured by natural

teeth that had been inserted to replace a missing tooth in the aesthetic zone (de-

fined as the region from teeth 15-25 and teeth 35-45). The included studies suggest

that such a therapy will lead to a successful outcome on, at least, the short term

with regard to implant survival, marginal peri-implant bone loss and incidence of

complications. A meta-analysis revealed an implant survival rate of 95.5 % after

one year (based on 19 studies) and only a little amount of marginal bone loss at

one year after definitive crown placement (0.20 mm, based on five studies). A low

number of complications was reported, most of which were minor and could be

solved non-invasively. These favorable results need closer scrutiny, since the availa-

ble literature showed several shortcomings. First, studies on single-tooth implants

in the aesthetic zone underexposed significant variables as soft tissue aspects, aes-

thetic outcome and patient satisfaction. Variables reflecting the condition of the

peri-implant mucosa as probing pocket depth, bleeding on probing and plaque

indices were lacking in most of the studies. Furthermore, the few studies that did

evaluate soft tissue appearance made use of the papilla index according to Jemt

(1997) to express the volume of the interproximal papillae or assessed the level of

the facial peri-implant mucosa. Although these outcome measures contribute to

the final aesthetic outcome, other aesthetically relevant items as soft tissue colour,

texture and contour were not taken into account. To assess the aesthetic outcome,

all aesthetically relevant aspects should be considered. For this purpose, objective

rating instruments as the Implant Crown Aesthetic Index (Meijer et al. 2005) and

the Pink Esthetic Score –White Esthetic Score (Belser et al. 2009) were introduced.

Besides the aesthetics of the mucosa, these indexes also contemplate the aesthet-

ics of the implant crown.

The design of the included studies should be considered as another shortcom-

ing. There was a lack of well-designed clinical trials and most of the studies could

be classified as case series. Since case series are prone to selection bias, results

of these studies should be interpreted with caution. Furthermore, in most of the

studies, sample sizes were small and follow-up periods were too short to draw

firm conclusions regarding the treatment outcome of single implant therapy on

the long term.

From the perspective of these abovementioned shortcomings, it seems para-

doxical that instead of establishing conventional treatment strategies, most of

the studies inquired into protocols where implants were inserted in fresh or early

healed extraction sites or were subjected to immediate or early loading. Despite

promising results for this variety of studies, there was too little evidence to an-

swer the question whether all these treatment strategies will result in a compara-

ble – or even better – outcome than the conventional procedures. Unfortunately,

no clinical trials could be retrieved focussing on different implant types or differ-

ent implant neck designs in particular.


the aesthetic zone

The aim of this study, as described in chapters 3 and 4, was to compare the out-

come of single-tooth implants in the maxillary aesthetic zone (from teeth 14 - 24)

with three different neck designs, namely a smooth ‘machined’ neck (‘smooth

group’), a rough neck with grooves (‘rough group’) and a scalloped neck with

grooves (‘scalloped group’). Variables were marginal bone level change, clinical

and aesthetic outcome measures and patient satisfaction.

Marginal bone level changeAfter implant placement and through time of function, it is commonly accepted

that implants will display some extent of bone loss (Albrektsson et al. 1986, Lau-

rell & Lundgren 2009). We considered loss of peri-implant marginal bone meas-

ured radiographically as being an important outcome measure expressing the

quality of the treatment outcome. First, marginal bone loss may induce pocket

formation which could be unfavorable for long-term health of the peri-implant

tissues (Rams et al. 1984, Heydenrijk et al. 2002). Second, loss of peri-implant

marginal bone might result in recession of the peri-implant mucosal level (Ben-

gazi et al. 1996, Chang et al. 1999b, Hermann et al. 2001a) thereby affecting the

aesthetic outcome.

Measurement of marginal bone on peri-apical radiographs is generally accepted

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as a reliable and feasible instrument to measure bone loss at least at the proximal

side of the implant (Hermann et al. 2001b, Salvi & Lang 2004) and offers fixed

reference points from the moment of implant placement to years thereafter, allow-

ing for longitudinal research. Since it is known that peri-implant bone loss occurs

circumferentially thus at the facial and palatal aspects as well (Buser et al. 2004,

Cardaropoli et al. 2006), radiographic bone loss observed at the proximal implant

side might be a measure for bone loss at the facial and palatal sides as well.

In our study, implants with a scalloped implant neck displayed significantly

more peri-implant bone loss from implant placement up to the end of follow up

(18 months after implant placement; 2.01 ± 0.77 mm) than the implants with a

smooth (1.19 mm ± 0.82 mm) and rough neck (0.90 ± 0.57 mm) but with com-

mon flat platforms (Chapter 3). Unfortunately, studies on the scalloped implant

are scarce and clinical trials are lacking, which limits a comparison of our results

with results from the literature. The available publications are in line with our find-

ings since values of 1.5 to 2.1 mm bone loss (standard deviations around 1 mm)

between implant placement and 12 months thereafter were reported (Nowzari et

al. 2006, Kan et al. 2007, McAllister 2007).

We do not have a clear explanation for the amount of bone loss in the scal-

loped group as observed in our study. One reason might be that peri-implant

bone is mainly formed in a horizontal plane. As a result, the more crestally related

facial and palatal part of the implant platform dictates the marginal bone level

around the implant. Another reason could be inferred from a biomechanical point

of view. Too much stress at the implant neck after loading, might induce initial

marginal bone resorption (Oh et al. 2002; Schrotenboer et al. 2008). Possibly, the

stress distribution from the scalloped implant to the bone was unfavorable and

too high, leading to the amount of marginal bone loss as was observed during the

first evaluation period. In this context, the complex connection between implant

and abutment could play a role.

Several studies demonstrated that a rough surface topography at the implant

neck exhibit less marginal bone resorption than a smooth coronal area (Shin et

al. 2006, Bratu et al. 2009, Nickenig et al. 2009) and that (micro)threads at the

level of the implant neck have the quality to preserve marginal bone (Palmer et

al. 2000, Shin et al. 2006, Lee et al. 2007). In contrast to these observations,

we could not detect a significant difference in bone loss between implants with

a rough or smooth neck (Chapter 3). However, since the abovementioned stud-

ies retrieved data mostly from posterior tooth replacements or from non-clinical

research, it is questionable whether these data can be extrapolated to our human

study involving maxillary teeth in the aesthetic zone. Unfortunately, clinical trials

investigating smooth and rough implant neck architectures for anterior single-

tooth replacements are lacking.

Since in our study the implant-abutment interface was closely related to the

bone crest (all implant necks were leveled with the bone crest at the time of im-

plant placement), it might be possible that the thought beneficial effect of a rough

implant neck, could not be effectuated at a level surpassing the bone resorption

around a smooth implant neck. This hypothesis is in line with suggestions from

the literature mentioning that the position of the implant-abutment interface rela-

tive to the bone crest at the time of implant placement is a significant factor de-

termining marginal bone loss (Hermann et al. 2000, Broggini et al. 2006, Jung

et al. 2008). An inflammatory reaction at the implant-abutment interface due to

microbial leakage seems to be a major factor for this bone loss. A more apical

position of the implant-abutment interface is thought to be a factor increasing the

inflammatory reaction (Broggini et al. 2006). Furthermore, a zone of connective

tissue will form between the bone crest and the inflammatory cell infiltrate at the

implant-abutment interface at the cost of marginal bone (Schwarz et al. 2008).

Other implant features might also be important in preventing bone loss. It has

been suggested that besides surface roughness and grooves, a conical internal

implant-abutment connection combined with a non-matching implant-abutment

diameter favor marginal bone preservation (Wennstrom et al. 2005, Jung et al.

2008, Cochran et al. 2009). It seems that by reducing the diameter of the abut-

ment, the implant-abutment interface and thereby the inflammatory reaction will

be displaced further away from the bone, resulting in less marginal bone loss.

Furthermore, an internal conical connection has been associated with a more

stable connection possibly leading to less bacterial leakage and a better stress

distribution (Hansson 2003, Coelho et al. 2008, Cochran et al. 2009). However,

the beneficial effects of such connections need further clinical investigation.

Clinical outcomeAt 18 months post-implant placement, significantly deeper pocket depths were

measured in the scalloped group together with higher bleeding scores compared

to the other study groups (Chapter 3). This is not a surprising finding when tak-

ing into consideration the higher amount of marginal bone loss in the scalloped

group and the positive correlation that was found between pocket depth and

marginal bone level alterations. From 6 to 18 months, pocket depths and bleed-

ing scores increased significantly in the scalloped group, while in this evaluation

period only a small amount of marginal bone loss was observed in this study

group. Apparently, the peri-implant tissues in the scalloped group developed

more marginal inflammation with time as confirmed by the higher bleeding

scores. As described by Schou et al. (2002), even a mild marginal inflammation

is associated with a deeper penetration of the probe. This might be a reason

that deeper pockets depths were measured at 18 months of follow-up, without

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observing a concordant loss of marginal bone loss. Furthermore, inflammation-

induced swelling of the peri-implant mucosa might have resulted in increased

pockets depth (‘pseudo-pocket’). Although there is no evidence showing a cor-

relation between pocket depth and the presence or absence of active peri-implant

disease (Schropp et al. 2005b, Heitz-Mayfield 2008), it has been shown that with

increasing pocket depth, an environment is created for periodontal pathogens

(Rams et al. 1984, Heydenrijk et al. 2002). We therefore believe that peri-implant

pocket depths should be limited and remain stable over time to facilitate healthy

peri-implant tissues. The long-term influence of increased pocket depth on mar-

ginal bone levels needs further study as applies to the interaction between mar-

ginal bone loss and pocket formation.

After placement of the definitive crown (6 months post-implant placement) to

1 year thereafter (18 months post-implant placement) the levels of the mid-facial

peri-implant mucosa remained stable (Chapter 3). This corresponded to the small

amount of marginal bone loss observed in this period. Despite this small amount

of bone loss, the level of the papillae gained some height after definitive crown

placement (overall 0.22 mm). The capacity of papillae to exhibit regrowth after

crown placement has also been observed in other single-tooth implant studies

(Jemt & Lekholm 2003, Schropp et al. 2005a, Den Hartog et al. 2008, Meijndert et

al. 2008). The study by Meijndert et al. (2008) in which a comparable restoration

procedure and the same evaluation strategy were used, reported a comparable

gain in papillary height of 0.25 mm.

To elucidate the effect of marginal bone loss on the level of the mucosa around

anterior single-tooth implants, it would have been of interest to compare the to-

tal amount of bone loss after 18 months with the total change in peri-implant

mucosal level. However, changes of the peri-implant mucosal level can only be

measured accurately after placement of the definitive crown (i.e. after six months

post-implant placement) since thereafter the actual peri-implant mucosal level is

established. After definitive crown placement, only minor marginal bone loss and

a concordant change in peri-implant mucosal level was observed. Since the most

bone loss already occurred during the first evaluation period, the true effect of

bone loss on the peri-implant mucosal level might have been missed.

Scalloped implants were accompanied by more complications of the defini-

tive crown, viz. porcelain fracture (six cases) and mobility (three cases), than

the other implants (Chapter 3). The complex connection between the scalloped

implant neck and abutment might have been a major factor determining these

complications. However, long-term follow-up is needed to unveil the stability of

the prosthetic restorations as the problems with the scalloped implant restora-

tions might mainly be an early phenomenon.

In the line of complications, an interesting phenomenon we encountered was a

trauma to an implant crown in one of our patients allocated to the smooth group

(Chapter 7). It appeared that only the fixation screw was damaged, while the im-

plant, restoration and peri-implant tissues remained unharmend. Just an easy pros-

thetic retreatment was neccesary and a surgical retreatment was prevented. We

realize that the incidence of trauma to implant restorations is not high. However,

we favor designing suprastructures as such that these structures are the weakest

link in case of trauma, thereby preserving the implant and surrounding tissue.

Aesthetic outcome and patient satisfactionTo assess the aesthetic outcome, objective rating instruments are available, to

be used by dental professionals. These instruments are composed of different

aesthetically related items based on the anatomic form, colour and surface char-

acteristics of the peri-implant mucosa and implant crown. Such instruments fa-

cilitate instant or longitudinal assessment of the aesthetic outcome of different

treatment strategies and can be of value for a thorough analysis of the final out-

come in order to improve treatment aspects. However, since the patient is the

final user of implant therapy, the opinion of the patient is also of importance.

Questionnaires to be completed by the patient are commonly employed to assess

the subjective appreciation of the aesthetic outcome.

To our best knowledge, only two aesthetic rating instruments are nowadays

available to assess the aesthetics of the peri-implant mucosa and implant crown

(Meijer et al. 2005, Belser et al. 2009). In our study, both these instruments were

used, knowing that these instruments are not yet optimal. A major drawback is

that these instruments are not suitable to assess the pre-operative situation as

well. When the pre-operative situation can be assessed, this might be of value

to better understand the possible role of factors determining the final aesthetic

outcome. Furthermore, the instruments are not yet tested for their external valid-

ity and with respect to their internal validity, further development is necessary to

improve the reproducibility (as discussed in Chapter 4). The same applies to the

development of validated questionnaires to assess patient (aesthetic) satisfac-

tion. Nowadays, no such questionnaires are available.

Beforehand, we hypothesized that the design of the implant neck might have

an effect on the level of the peri-implant mucosa and with that influences the final

aesthetic outcome. However, using both the available aesthetic evaluation instru-

ments (Meijer et al. 2005, Belser et al. 2009), this effect could not be shown in our

study (Chapter 4). Although the scalloped implants displayed more radiographic

marginal bone loss, there were no differences between study groups regarding

the items ‘level of the facial peri-implant mucosa’ and ‘quantity of papillary tissue’

(both these items are part of the aesthetic evaluation instruments).

There are some possible reasons for not observing between-group differences

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on these items despite between-group differences in marginal bone loss. First, it

might be that the difference in marginal bone resorption between the scalloped

group and the other study groups brought about a clinical effect that was too lit-

tle to be observed with the aesthetic indexes we applied or that the indexes itself

were not able to reveal these differences (e.g., because of the shortcomings as

discussed earlier). A second reason might be ascribed to the role of the periodon-

tium of the adjacent teeth. Namely, it is assumed that the level of the papilla is

related to the bone level next to the adjacent teeth (Choquet et al. 2001, Kan et

al. 2003, Romeo et al. 2008). We observed only minor marginal bone loss at the

adjacent teeth without differences between study groups. Possibly, the periodon-

tium of the adjacent teeth also acts on the level of the facial peri-implant mucosa.

Finally, we believe that the role of the pre-operative situation for the final aesthet-

ic outcome needs discussion. Possibly, the level of the mucosa before implant

placement was more relevant to the future level of the peri-implant mucosa than

is the amount of bone loss around the implant neck. In our study, all implants

were placed in healed extraction sites, up to a third of which were augmented in a

separate session before implant placement. It revealed that in 63% of the cases,

the level of the facial peri-implant mucosa showed a deviation when compared to

the adjacent dentition. It is known that after tooth removal, the walls of the alveo-

lus undergo substantial resorption at the facial aspect, affecting the anatomy of

the soft tissue (Schropp et al. 2003a, Araujo & Lindhe 2005). A strategy of imme-

diate or early implant placement or a socket preservation technique might favor

the aesthetic outcome. By way of comparison, in other studies (Belser et al. 2009,

Buser et al. 2009) in which implants were installed in early healed extraction sites

and subjected to simultaneous guided bone regeneration, the level of the facial

peri-implant mucosa showed a deficiency in only 22 % and 10% of the cases, res-

pectively. As discussed earlier, it would be helpful to further develop an aesthetic

evaluation instrument, by which the pre-operative situation can be assessed as

well. This will facilitate a further exploration of predisposing factors.

Although from a professional’s perception the appearance of the peri-implant

mucosa and implant crown were not acceptable in, respectively, 40% and 20 % of

the overall cases, the subjective aesthetic appreciation of the patient was high.

The discrepancy between the aesthetic outcome from a professional’s and pa-he discrepancy between the aesthetic outcome from a professional’s and pa-discrepancy between the aesthetic outcome from a professional’s and pa-

tient’s perception has been reported in earlier studies (Chang et al. 1999a, Mei-

jndert et al. 2007, Esposito et al. 2009). As suggested by Chang (Chang et al.

1999a), it might be that factors considered by professionals to be relevant for

the aesthetic outcome may not be of decisive importance for patient’s aesthetic

satisfaction. Furthermore, we argue that for the final appreciation of the patient,

the pre-operative situation plays a role of significance and gives weight to the

final judgment. When the pre-operative situation is compromised and patient’s

expectations are realistic, patients might be satisfi ed even when the aesthetic out-might be satisfied even when the aesthetic out-

come according to an objective index is poor. The aesthetic indexes do not take

the preoperative situation into account as discussed before. The high general

patient satisfaction we observed might be deduced from the patient’s apprecia-

tion with the aesthetics, since the outcome of all questions was correlated with

general patient satisfaction. However, it should be noticed that also other aspects

as function and comfort might contribute to general patient satisfaction.

Immediate loading of single-tooth implants in the aesthetic zone

The objective of this study was to compare the outcome of immediate loading

with that of conventional loading of implants applied for a missing anterior maxil-

lary tooth for radiographic marginal bone level change and clinical and aesthetic

outcome measures together with patient satisfaction (Chapter 5). We hypothe-

sized that immediate loading is not inferior to conventional loading.

Marginal bone level changeIt seems rational to argue that immediate loading might induce more marginal

peri-implant bone loss than conventional loading, since immediate loading might

induce a more uneventful healing of the surrounding peri-implant bone. How-

ever, no differences were observed between immediate and conventional loading

regarding marginal bone loss at 6 and 18 months post-implant placement. This

is in agreement with recent studies on immediate and conventional single-tooth

implants in the anterior zone (Hall et al. 2007, Den Hartog et al. 2008, Degidi et

al. 2009).

Clinical outcomeStudies on immediate loading have often considered implant survival as the pri-

mary outcome measure. This is, however, only one outcome variable reflecting

a succeeding therapy. In our study, survival rates were 96.8% for the immediate

group (one implant failed) and 100% for the conventional group. These high

survival rates were confirmed by other studies on immediately loaded implants,

even when inserted in fresh extraction sockets (Den Hartog et al. 2008). It should

be realized that the sample size of our study was too small to demonstrate wheth-

er immediate loading was non-inferior to conventional loading with respect to

implant survival. Additional (long-term) studies would be helpful to draw firm

conclusions regarding the potential hazardous effect of immediate loading on

implant survival.

It is important to reach sufficient primary implant stability before performing

immediate loading. It has been observed that in addition to the anatomy of the

bone (Mesa et al. 2008, Roze et al. 2009) and preparation technique (Tabassum

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et al. 2010), the geometry (O’Sullivan et al. 2004, Dos Santos et al. 2009) and

length of the implant (Mesa et al. 2008) are factors influencing primary stabil-

ity. In our study, almost all implants were 16 mm in length, the longest avail-

able for the type of implant we used. Furthermore, the implants had a rough

surface topography and a tapered design, both favoring primary implant stability

(O’Sullivan et al. 2004, Dos Santos et al. 2009). It might be attributed to these

factors that in our study there were no difficulties to reach primary implant sta-

bility. Besides paying attention to sufficient primary stability as being a ‘conditio

sine qua non’ for immediate loading, it is also important to carefully instruct the

patient and to pay attention to the occlusion of the provisional crown. In our

study, all provisional crowns were free from centric and eccentric occlusal con-

tacts with the antagonist teeth.

With respect to the health of the peri-implant tissue expressed in probing

depth, bleeding upon probing and amount of plaque, no differences were noticed

between the immediate and conventional study group. The implants showed

deeper probing pockets depths than the adjacent teeth (as also was observed

in the implant neck study Chapter 3). Such deeper pocket depths around single-

tooth implants have been reported in another study from our research group

(Meijndert et al. 2008). It is argued that this difference in probing depth between

implants and natural teeth, might be partly ascribed to the anatomy of the peri-

implant mucosa and its attachment to the implant surface, being different com-

pared to the anatomy of the gingiva and its attachment to the root surface (Ber-

glundh et al. 1991). It was demonstrated that these differences had an impact on

probing depth measurements, since the gingiva was more resistant to probing

forces than the mucosal seal around implants (Ericsson & Lindhe, 1993).

Another interesting finding was the high number of implants displaying bleed-

ing upon probing. At 18 months post-implant placement, most of the implants

showed bleeding upon probing (around 80% of the implants versus 30% of the

adjacent teeth, including the implants from the implant neck study). Unfortu-

nately, data from other relevant studies on this topic are scarce and contradic-

tory values are reported (Den Hartog et al. 2008). Besides, bleeding index scores

were presented in percentages as well as in mean values or the unit of analysis

differed (per implant or per implant side). Since bleeding on probing indicates

presence of inflammation in the peri-implant mucosa (Heitz-Mayfield 2008), the

significance of this variable as predictor for the long-term prognosis needs further

investigation.

Aesthetic outcome and patient satisfactionThere is growing evidence that immediate loading of implants inserted in fresh

extraction sockets would lead to more favorable soft tissue levels compared to a

delayed strategy (Block et al. 2009, De Rouck et al. 2009). These studies reported

that immediate stabilization of the soft tissue after tooth removal by means of im-immediate stabilization of the soft tissue after tooth removal by means of im-

mediate implant placement and immediate placement of the provisional crown,

would result in 0.75 to 1 mm more soft tissue preservation mid-facially. In our

study, all implants were inserted in healed sites as was common those days. As

pointed out earlier, tooth removal induces resorption of the walls of the alveolus

affecting the soft tissue anatomy (Schropp et al. 2003b, Araujo & Lindhe 2005).

It could be that for healed sites, a potential positive effect of an immediate (pro-

visional) crown on soft tissue preservation subsided. When using the aesthetic

evaluation instruments to express soft tissue aesthetics, at least no significant

difference between immediate and conventionally loaded implants was observed.

The same applied to the volume of the papilla assessed with the papilla index.

General patient satisfaction was high in both study groups and patients were

satisfied regarding function, aesthetics and treatment procedure. Other studies

on anterior single-tooth implants reported comparable overall satisfaction scores

of 8.8 and higher (also using VAS) (Schropp et al. 2004, Den Hartog et al. 2008).

As confirmed by other studies (Levi et al. 2003, Schropp et al. 2004), a substan-

tial percentage of conventionally treated patients (30%) experienced the healing

time of the implant as long. Although Levi et al. (2003) found that treatment time

was not a critical factor for overall satisfaction, the shorter treatment time of im-

mediate loading might serve these patients.

Principal findings and clinical implicationsThe general aims of our study were to compare the outcome of single implants

with different neck designs applied to replace a missing anterior tooth in the max-

illa and to compare the outcome of immediate loading with conventional loading,

again for implants replacing a missing tooth in the anterior maxilla.

First, we assessed the treatment outcome of single-tooth implants in the max-

illary aesthetic zone with three different implant neck designs, namely a 1.5 mm

smooth implant neck (‘smooth group’), a moderately rough implant neck with

grooves (‘rough group’) and a scalloped moderately rough implant neck with

grooves (‘scalloped group’). At 18 months post-implant placement, the scalloped

group showed significantly more marginal bone loss, deeper probing pocket

depths and higher bleeding scores than the smooth group and rough group,

while there were no differences in outcome between the smooth group and rough

group. Besides, the implants in the smooth and rough groups revealed favorable

treatment outcomes in terms of bone loss, implant survival, complications and

soft tissue aspects, which are in line with values reported in other studies on

single-tooth implants placed in the anterior maxilla (Den Hartog et al. 2008).

Although there were no differences in aesthetic outcome between the three dif-

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ferent implants, we suggest the use of implants with a 1.5 mm smooth neck or a

rough neck with grooves for single anterior tooth replacements in stead of using

implants with a scalloped neck design since the latter implants displayed more

bone loss and less clinical performance.

Next, we assessed the treatment outcome of immediately loaded single-tooth

implants in the aesthetic zone. It revealed that - on the short term - immedi-

ate loading will lead to a treatment outcome that is not less favorable than con-

ventional loading. Since the concept of immediate loading shortens treatment

time and offers comfort for the patient, this concept should be considered as a

promising alternative to conventional loading. However, it should be realized that

the concept of immediate loading has to be performed according to a specified

protocol paying attention to adequate primary implant stability, a non-occluding

provisional crown and careful patient instruction. Moreover, only short term re-

sults are available thus far.

Future researchBased on our findings and that of other studies (Hall et al. 2007, Degidi 2009),

immediate loading of a single-tooth implant in the aesthetic zone can be consid-

ered as an effective treatment strategy on the short term. Additional studies are

needed to investigate the efficacy of immediate loading on the long-term, before

immediate loading can indeed be considered as an at least equal treatment mo-

dality as conventional loading has been shown to be.

Next to immediate loading, the promising concepts of immediate and early

implant placement after tooth extraction need further study. In our immediate

loading study, all implants were installed in healed extraction sites, at least three

months after the tooth had been extracted. However, placement of an implant im-

mediately or early after tooth extraction has been posed to be beneficial for pres-

ervation of hard and soft tissue. Furthermore, when immediate or early placed

implants are subjected to immediate loading, this could offer even more com-

fort for the patient than just applying immediate loading. In order to gain more

insight into preservation of hard and soft tissue after tooth extraction, studies

are needed investigating socket preservation techniques and - whether or not

- these techniques should be combined with immediate or early implant place-

ment. Socket preservation techniques could, amongst others, enhance the final

outcome since collapse of tissue might be prevented and with that a thorough

augmentation procedure.

As applies to our immediate loading study, additional (long-term) studies are

needed to validate the conclusions we draw in our study to different implant

neck designs. Furthermore, besides focusing on the topography and geometry

of the implant neck, additional research on other material aspects is needed.

For instance, the promising concept of internal conical connections between im-

plant and abutment needs further study as holds for the concept of non-matching

implant-abutment diameters (‘platform switching’).

An important starting point for future research is that studies should focus on

the quality of the outcome, using uniform outcome variables and data presenta-

tion. This will ease comparison of studies. In order to compare different types of

interventions, clinical trials are needed with sufficiently large study populations

and random allocation procedures. Furthermore, we believe that it would be help-

ful to consider the pre-operative situation and its relation to the final outcome as

well. When taking the pre-operative situation into account too, the true effect of

an intervention on the final outcome might be determined with more accuracy

meanwhile reducing the difference in treatment outcome as rated by the clini-

cian (who now just rates the appearance of the crown and soft tissue) and the

patient (who also includes the baseline characteristics in his ratings). With regard

to the measurement instruments, efforts should be made to further develop an

objective aesthetic rating instrument with good internal and external validity, to

be commonly used in implant research. The present aesthetic rating instruments

are only tested for their reproducibility and do not take the pre-operative situation

into account. The same applies to the development of a validated questionnaire

assessing patient satisfaction. Finally, upcoming instruments as three-dimen-

sional imaging techniques could be brought into new research projects. With

such measurement instruments, the effect of an intervention on the hard and

soft peri-implant tissues can be assessed in all dimensions with more ease and

probably with more accuracy.

It is foreseen that, through further research, more insight will be obtained into

the efficacy and efficiency of implant treatment strategies to replace a missing

anterior tooth. This will favor the ultimate ambition to strive for, viz. efficient

creation of a high quality restoration for the long term, satisfying the criteria that

reflect function and aesthetics.

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Summary

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summary A lost or congenitally missing tooth in the anterior region (‘aesthetic zone’) usu-

ally requires prosthetic replacement for functional and aesthetic reasons. The

ultimate goal to strive for when restoring a missing anterior tooth is creation

of a high quality restoration for the long-term, satisfying the criteria that reflect

function and aesthetics. Dental implants have conquered a prominent role in

contemporary dentistry when it comes to such replacements.

There are, however, factors that could affect the treatment outcome of single-

tooth implants in the aesthetic zone. E.g., after implant placement and through

time of function, it is accepted that some marginal bone around the implant will be

lost. The level of the peri-implant marginal bone is related to the level of the peri-im-

plant mucosa, which, in turn, is commonly considered as an important aspect de-

termining the aesthetic outcome. Hence, loss of peri-implant marginal bone could

affect the level of the peri-implant mucosa and with that the aesthetic outcome.

Furthermore, marginal peri-implant bone loss might induce pocket formation,

which could be unfavorable for long-term health of the peri-implant tissue. There

is some evidence that the design of the implant neck might influence the amount

of peri-implant marginal bone loss. As a result, various implant neck designs have

been introduced for maximum preservation of marginal peri-implant bone.

Apart from the role of the implant neck design, the concept of immediate load-

ing is object of study in recent implantology. Placement of an implant crown im-

mediately after implant installation offers advantages for the patients compared

to a conventional load-free healing period of several months. These include reduc-

tion of overall treatment time, avoidance of second-stage surgery and immediate

comfort as there is no need for a removable prosthesis during the healing phase.

However, immediate loading might also induce more risk, since the implant is dis-

turbed by forces during healing, possibly affecting a successful osseointegration.

There is a paucity of well-designed trials addressing the effect of the implant

neck design on the outcome of single-tooth implants therapy in the aesthetic

zone. The same applies to trials investigating the efficacy of immediate loading

of single-tooth implants in the aesthetic zone. Therefore, the general aims of this

thesis were to compare the outcome of single-tooth implants in the aesthetic

zone with three different neck designs and to compare the outcome of immedi-

ate loading with that of conventional loading, also for single-tooth implants in

the aesthetic zone.

In chapter 2 the available literature on the efficacy of single-tooth implant ther-

apy in the aesthetic zone is systematically reviewed. Studies reporting on implants

replacing a missing anterior tooth (region 15-25) with natural adjacent teeth were

considered for inclusion. A distinction was drawn between immediate, early and

conventional implant approaches. The methodological quality of eligible studies

was assessed by two reviewers independently using specific study-design related

assessment forms.

Out of 86 primarily selected articles, 19 studies fulfilled the inclusion criteria.

Follow-up periods of included studies were relatively short (only four studies had

a follow-up duration ≥ five years). A meta-analysis showed an overall implant

survival rate of 95.5% (95% CI: [93.0 – 97.1]) after one year and minor marginal

bone loss at one year after definitive crown placement (0.20 mm, based on five

studies). A stratified meta-analysis revealed no differences in survival between

immediate, early and conventional implant strategies. A low incidence of biologi-

cal and technical complications was found. No differences in outcome measures

were reported in clinical trials comparing immediate, early or conventional im-

plant strategies. Unfortunately, no studies could be identified focussing on the

effect of different implant neck designs or different implant types.

This review demonstrates that promising short-term results can be achieved

for immediate, early and conventional single-tooth implant treatment in the

aesthetic zone. However, it was found that in literature, important parameters

including aesthetic outcome, soft-tissue aspects and patient satisfaction were

clearly underexposed. The question whether immediate and early single-tooth im-

plant procedures will result in comparable - or even better - treatment outcomes

could not be answered due to lack of well-designed controlled clinical studies.

The same applies to the question regarding the effect of the design of the implant

neck on the outcome of therapy.

In chapters 3 and 4, the outcomes of single-tooth implants in the aesthetic

zone with three different neck designs are compared for marginal bone level

changes, clinical outcome measures, aesthetic outcome and patient satisfaction.

A total number of 93 patients with a missing anterior tooth in the maxilla was

randomly assigned to be treated with an implant with a 1.5 mm smooth neck

(‘smooth group’), with a moderately rough neck with grooves (‘rough group’)

or with a scalloped moderately rough neck with grooves (‘scalloped-group’). All

implants were installed in healed sites and were loaded after three months with

a provisional crown. Three months later, implants were restored with definitive

all-ceramic crowns. After implant placement and at 6 and 18 months thereafter,

clinical data and standardized radiographs and photographs were collected. Pa-

tient satisfaction was explored using a self-administered questionnaire.

Chapter 3 focuses on marginal bone level changes and clinical outcome. Sig-

nificant differences in radiographic marginal bone loss were found between the

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study groups. The scalloped group yielded significantly more radiographic bone

loss from implant placement to 18 months thereafter (2.01 ± 0.77 mm) compared

to the smooth group (1.19 ± 0.82 mm) and rough group (0.90 ± 0.57 mm). Fur-

thermore, at 18 months follow-up, the scalloped group showed significantly deep-

er pocket depths and significantly higher bleeding scores. Besides, more compli-

cations of technical origin (e.g. porcelain fracture, crown mobility) occurred in

the scalloped group during follow-up. Survival rates were 96.8% for the smooth

group (1 implant lost) and 100% for the rough and scalloped groups. There were

no significant differences in bone loss and clinical outcome between the smooth

group and rough group and both these study groups showed favorable results as

compared to what has been established in other studies on single-tooth implants

in the aesthetic zone. Based on these findings, we recommend the use of either

an implant with a 1.5 mm smooth neck or an implant with a rough neck with

grooves for anterior single-tooth replacements in stead of using an implant with

a scalloped neck design.

Chapter 4 focuses on the aesthetic outcome from a professional’s and patient’s

perception. On photographs taken at one year after definitive crown placement

(18 months post implant placement), the aesthetic outcome was assessed by two

professionals using two objective aesthetic indexes (Pink Esthetic Score/White Es-

thetic Score (PES/WES) and Implant Crown Aesthetic Index (ICAI)). A 5-point Likert

scale, ranging from very dissatisfied to very satisfied, was used to assess the aes-

thetic outcome from a patient’s perception. Furthermore, general patient satisfac-

tion was explored using a Visual Analogue Scale ranging from 0 (very dissatisfied)

to 10 (very satisfied). No differences in aesthetic outcome were found between the

three implant neck designs. According to the professional’s assessments using the

PES/WES and ICAI, respectively 79.3% and 62% of the crowns showed acceptable

aesthetics. In 59.8% and 56.5% of the cases, acceptable mucosa aesthetics were

found according to PES/WES and ICAI, respectively. A regression analysis showed

that a pre-implant augmentation procedure was associated with less favorable ob-

jective aesthetics of the mucosa (according to the PES/WES, the most reproducible

index). From a patient’s perception, more than 80% of the patients were satisfied

about the aesthetic outcome of the crown and mucosa. This finding revealed that

there is a discrepancy between the aesthetic appreciation from a professional’s and

patient’s perception. General patient satisfaction was high (9.0 ± 1.0 out of a maxi-

mum of 10). This study shows that the aesthetic outcome of single-tooth implants

in the aesthetic zone appears to be independent on the implant neck designs ap-

plied, but dependent on the need for pre-implant augmentation surgery.

In chapter 5 it is studied whether immediate loading of anterior single-tooth im-

plants is not inferior to conventional loading. A number of 62 patients with a sin-

gle missing maxillary anterior tooth was randomly assigned to two study groups.

In one study group, patients were treated with an implant that was restored with a

non-occluding provisional crown within 24 hours (‘immediate group’). In the oth-

er study group, patients were treated with an implant that was restored according

to a two-stage procedure at three months after implant placement (‘conventional

group’). After the provisional phase, definitive all-ceramic crowns were made.

Follow-up visits were conducted after 6 and 18 months post-implant placement.

The primary outcome measure of this study was marginal bone level change as

measured on standardised radiographs. Non-inferiority of immediate to conven-

tional loading was considered established when the immediately loaded implants

showed no more than 0.5 mm of mean marginal bone loss compared to con-

ventionally loaded implants. Other outcome measures were survival, soft tissue

aspects (probing pocket depth, plaque, bleeding, peri-implant mucosal level),

aesthetic outcome (using PES/WES and ICAI) and patient satisfaction.

All implants had good primary stability (≥ 45 Ncm insertion torque). At 18

months post-implant placement, no differences in marginal bone loss were found

(immediate group 0.91 ± 0.61 mm, conventional group 0.90 ± 0.57 mm). One

implant was lost in the immediate group, three weeks after immediately loaded

with a provisional crown. No implants were lost in the conventional group. There

were no differences in probing pocket depth, plaque, bleeding and peri-implant

mucosal level. Furthermore, the aesthetic outcome and patient satisfaction did

not differ between both study groups.

Within the limitations of this study (sample size and follow-up duration), we

conclude that immediate loading of single-tooth implants in the aesthetic zone

is not less favorable than conventional loading. Since the concept of immediate

loading offers advantages for the patient, this concept should be considered as a

promising alternative to conventional loading. However, the concept of immedi-

ate loading has to be performed according to a specified protocol paying atten-

tion to adequate primary implant stability, a non-occluding provisional crown and

careful patient instruction.

An immediate loading protocol of an anterior single-tooth implant is descri-

bed in chapter 6. It is described how the provisional crown was made and how an

optimal emergence profile was created by adjusting the provisional restoration.

After the provisional phase, an impression was made with an individually fabrica-

ted impression post for an accurate reproduction of the established emergence

profile. The final crown was a screw-retained all-ceramic crown consisting of an

individual zirconia abutment. By implementing this protocol, an optimal defini-

tive result could be achieved together with immediate patient satisfaction.

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In chapter 7 a report of a trauma case is described in which an implant crown

in the aesthetic zone was involved. The traumatic impact resulted in a palatal

displacement of the implant crown. After careful examination and follow-up, it

appeared that only the fixation screw was damaged, while the implant, crown

and peri-implant tissues remained unharmed. The implant crown could easily be

replaced on the implant using a new fixation screw.

The main research outcomes are discussed and general conclusions are drawn

in chapter 8. It is concluded that for single-tooth replacements in the aesthetic

zone, implants with a 1.5 mm smooth neck or a rough neck with grooves display

less marginal bone loss and better clinical performance than implants with a

scalloped rough neck with grooves. However, there were no differences in aes-

thetic outcome between the various types of implants studied. Furthermore, we

conclude that the outcome of immediate loading of single-tooth implants in the

aesthetic zone is not less favorable than conventional loading. Additional follow-

up studies are needed to validate these conclusions for the long-term.

samenvattingBij het verloren gaan van een gebitselement of wanneer deze nooit is aangelegd,

bestaat vaak behoefte aan prothetisch herstel. Dit geldt in het bijzonder wanneer

het een gebitselement betreft in het zichtbare deel van het gebit, de zogenaamde

esthetische zone. Het ultieme doel van prothetisch herstel is het realiseren van

een duurzame kunsttand, die qua functie en esthetiek niet onder doet voor een

natuurlijk gebitselement. In de hedendaagse tandheelkunde hebben implantaten

een prominente rol verworven bij de vervanging van een ontbrekend gebitsele-

ment. Een implantaat is een kunstwortel die in het kaakbot wordt geplaatst en

hierin vastgroeit. Op een implantaat kan vervolgens een kroon worden geplaatst,

waarmee het ontbrekende gebitselement adequaat is vervangen. Een implantaat

die een enkel gebitselement vervangt, wordt ook wel een solitair implantaat ge-

noemd.

Nadat een implantaat in het kaakbot is geplaatst, verdwijnt vaak een beetje bot

rond de hals van het implantaat. Dit zogenaamde peri-implantaire bot is belang-

rijk voor de hoogte van het tandvlees rond het implantaat (de peri-implantaire

mucosa). Wanneer peri-implantair bot verloren gaat, kan de peri-implantaire mu-

cosa zich terugtrekken. Bij de vervanging van een gebitselement in de esthetische

zone, is niet alleen het uiterlijk van de kroon van belang, maar ook het uiterlijk

van het omliggende tandvlees. Immers, bij lachen en praten is het tandvlees in

de esthetische zone soms zichtbaar. Wanneer de peri-implantaire mucosa zich

terugtrekt en qua niveau afwijkt van het tandvlees rond de natuurlijke tanden,

resulteert dit in een minder fraai esthetisch resultaat. Verder kan verlies van mar-

ginaal peri-implantair bot leiden tot een diepere pocket tussen het implantaat en

de peri-implantaire mucosa. Een pocket is een spleet tussen de peri-implantaire

mucosa en het implantaat, die ook aanwezig is tussen natuurlijke gebitselemen-

ten en tandvlees. Als de pocket dieper wordt, kan dit leiden tot minder gezond

peri-implantair weefsel, omdat schadelijke bacteriën beter gedijen in diepere poc-

kets. Het is aangetoond dat de vorm en oppervlaktestructuur van de hals van het

implantaat van invloed zijn op het verlies aan peri-implantair bot en dat bij som-

mige typen implantaathalzen minder peri-implantair botverlies optreedt. Deze

bevinding heeft geleid tot de introductie van diverse typen implantaathalzen voor

maximaal behoud van het peri-implantaire bot.

Naast het type implantaathals, heeft het concept van direct belasten de aan-

dacht in de hedendaagse implantologie. Bij dit concept wordt kort nadat het im-

plantaat in het kaakbot is geplaatst, een kroon op het implantaat gezet (binnen

48 uur voor de benaming ‘direct belasten’). Het implantaat wordt dus via de

kroon direct belast, bijvoorbeeld door contact met voedsel en druk van de lip

en tong. Dit in tegenstelling tot het gebruikelijke concept van conventioneel be-

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lasten, waarbij het implantaat gedurende drie maanden ongestoord vastgroeit.

Daarna volgt plaatsing van de kroon op het implantaat. Direct belasten biedt

voordelen voor de patiënt, zoals een kortere behandelduur en direct comfort,

omdat de kroon direct wordt geplaatst. Echter, het concept van direct belasten

brengt ook een risico met zich mee, omdat het implantaat belast wordt tijdens

het proces van vastgroeien in het kaakbot. Het implantaat kan hierdoor mogelijk

verloren gaan.

Tot op heden zijn slechts weinig klinische studies verricht naar solitaire im-

plantaten in de esthetische zone waarbij gekeken werd naar het effect van het

type implantaathals op het eindresultaat. Dit geldt tevens voor het resultaat van

direct belasten van solitaire implantaten in de esthetische zone. In dit promotie-

onderzoek is daarom het behandelresultaat van drie verschillende typen implan-

taathalzen vergeleken bij solitaire implantaten in de esthetische zone. Daarnaast

is het concept van direct belasten onderzocht, wederom toegepast bij solitaire

implantaten in de esthetische zone. Dit concept is vergeleken met het behandel-

resultaat van conventioneel belasten.

Hoofdstuk 2 betreft een systematische literatuurstudie naar het resultaat van

implantaten in de esthetische zone (tot de tweede premolaar). Studies naar de

uitkomsten van solitaire implantaten geplaatst tussen twee natuurlijke buurele-

menten kwamen in aanmerking voor inclusie. Er werd onderscheid gemaakt tus-

sen solitaire implantaten die direct, vroeg (< drie maanden na implanteren) of

conventioneel werden belast. De methodologische kwaliteit van geschikte stu-

dies werd beoordeeld door twee beoordelaars, onafhankelijk van elkaar en aan de

hand van een vaste set criteria.

Van de 86 primair geselecteerde artikelen, bleken 19 studies te voldoen aan de

vooraf opgestelde in- en exclusiecriteria. De follow-up periodes van het meren-

deel van de geïncludeerde studies bleek relatief kort te zijn; slechts in 4 studies

bedroeg de follow-up ≥ vijf jaar). Een meta-analyse liet een implantaat-overle-

vingspercentage zien van 95,5% na één jaar (95% betrouwbaarheidsinterval 93,0

– 97,1) en bovendien bleek weinig peri-implantair botverlies na plaatsen van de

definitieve kroon op te treden (0,20 mm, gebaseerd op vijf studies). Een gestrati-

ficeerde meta-analyse toonde geen verschil aan in overleving tussen direct, vroeg

en conventioneel belaste implantaten. Er was een lage incidentie van klinische

complicaties (b.v. peri-implantitis) en complicaties van technische aard (b.v.

breuk van de kroon). Helaas werden geen studies in de literatuur aangetroffen,

die het effect van het type implantaathals op het behandelresultaat onderzoch-

ten.

De conclusie van deze literatuurstudie is dat – in ieder geval voor de korte

termijn – de behandelresultaten van zowel direct, vroeg als conventioneel belaste

solitaire implantaten in de esthetische zone veelbelovend zijn. Belangrijke varia-

belen als het esthetische resultaat, aspecten van de peri-implantaire mucosa en

patiënttevredenheid moeten nog nader worden onderzocht. De vraag of direct en

vroeg belasten tot vergelijkbare – of zelfs betere – behandelresultaten leiden dan

conventioneel belasten, kon niet worden beantwoord wegens gebrek aan goede

gecontroleerde studies. Hetzelfde geldt voor de vraag wat het effect is van het

type implantaathals op het behandelresultaat.

In hoofdstuk 3 en 4 wordt het behandelresultaat beschreven van de toepassing

van drie verschillende implantaathalzen bij solitaire implantaten in de estheti-

sche zone. De onderzochte variabelen waren marginaal peri-implantair botver-

lies, klinisch en esthetisch resultaat, en patiënttevredenheid. Er werden 93 patiën-

ten geïncludeerd met een ontbrekend gebitselement in de esthetische zone. De

patiënten werden at random verdeeld over drie studiegroepen voor een behande-

ling met een implantaat met een 1.5 mm gladde hals (‘gladde groep’), een matig-

ruwe hals met groeven (‘ruwe groep’) of met een gewelfde, matig-ruwe hals met

groeven (‘gewelfde groep’). Alle implantaten werden minimaal drie maanden na

extractie geplaatst. De implantaten werden na drie maanden voorzien van een

tijdelijke kroon. Deze tijdelijke kroon werd na drie maanden vervangen door een

volledig keramische definitieve kroon. Direct na plaatsen van het implantaat en

na 6 en 18 maanden, werden klinische data verzameld en gestandaardiseerde

röntgenopnamen en lichtbeelden gemaakt. De patiënttevredenheid werd onder-

zocht met behulp van een vragenlijst.

In hoofdstuk 3 wordt ingegaan op de variabelen marginaal peri-implantair

botverlies en klinisch resultaat. De gewelfde groep vertoonde significant meer

marginaal botverlies na plaatsen van het implantaat tot 18 maanden daarna (2.01

± 0.77 mm) vergeleken met de gladde groep (1.19 ± 0.82 mm) en ruwe groep

(0.90 ± 0.57 mm). Verder vertoonden de implantaten in de gewelfde groep sig-

nificant diepere pocketdiepten, significant meer bloeding na sonderen en wer-

den meer complicaties waargenomen van technische aard (losse kroon, breuk

van porselein). De implantaat-overlevingspercentages bedroegen 96,8 % in de

gladde groep (één implantaat ging verloren) en 100% in de ruwe en gewelfde

groep. Tussen de gladde groep en ruwe groep waren geen significant verschillen

in botverlies en klinisch resultaat waarneembaar. Beide studiegroepen vertoon-

den gunstige resultaten in vergelijken met andere studies uit de literatuur. Voor

de vervanging van een gebitselement in de esthetische zone wordt dan ook een

implantaat met een gladde hals of met een ruwe hals aangeraden en niet een

implantaat met een gewelfde hals, omdat er bij laatstgenoemde type implantaat

meer botverlies en een minder klinische resultaat werd waargenomen.

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In hoofdstuk 4 wordt het esthetische resultaat van de drie verschillende hals-

typen beschreven vanuit zowel het perspectief van de professional als vanuit het

perspectief van de patiënt. Zowel het esthetisch resultaat van de kroon als de peri-

implantaire mucosa werd beoordeeld. Op foto’s, genomen na 1 jaar van plaatsen

van de definitieve kroon (18 maanden na plaatsen van het implantaat), werd door

twee professionals het esthetisch resultaat beoordeeld aan de hand van twee

objectieve indexen (de Pink Esthetic Score-White Esthetic Score (PES-WES) en

de Implant Crown Aesthetic Index (ICAI)). Een 5-punts schaal, lopend van zeer

ontevreden tot zeer tevreden, werd gebruikt voor de beoordeling van het esthe-

tisch resultaat door de patiënt. De algemene tevredenheid van de patiënt over het

resultaat van de behandeling, werd gemeten met behulp van een schaal, lopend

van zeer ontevreden (score 0) tot zeer tevreden (10). Er bleek geen verschil in het

esthetisch resultaat van de drie verschillende typen implantaathalzen. Volgens de

professionals waren respectievelijk 79.3% en 62% van de kronen esthetisch ac-

ceptabel, gemeten met de meetinstrumenten PES-WES en ICAI. De mucosa bleek

in 59.8% en 56.5% esthetisch acceptabel. Een regressie-analyse toonde aan dat

een pre-implantologische bot-opbouw (i.v.m. een botdefect) leidt tot een slechter

esthetisch aanzicht van de peri-implantaire mucosa. Meer dan 80% van de pa-

tiënten bleek tevreden te zijn over de esthetiek van de kroon en peri-implantaire

mucosa. Hieruit blijkt een verschil tussen de opinie van de professional en de

opinie van de patiënt. De algemene tevredenheid van de patiënten was hoog

(9.0 ± 1.0, gemeten met een visueel analoge schaal). Op basis van de resultaten

van deze studie wordt geconcludeerd dat het esthetisch resultaat van solitaire

implantaten niet afhankelijk is van het type hals van het implantaat, maar wel van

een pre-implantologische bot-opbouw.

In hoofdstuk 5 wordt de uitkomst van direct belasten van solitaire implantaten

in de esthetische zone beschreven. Er werd nagegaan of deze uitkomst onder-

doet voor een concept waarbij de implantaten conventioneel worden belast. Er

werden 62 patiënten met een missend frontelement in de bovenkaak at random

toegewezen aan twee studiegroepen. In de ene studiegroep werden patiënten

behandeld met een implantaat die binnen 24 uur werd voorzien van een tijdelijke

kroon. Deze kroon had geen contact met de gebitselementen in de onderkaak,

d.w.z. deze kroon was uit de occlusie (directe groep). In de andere studiegroep

werd het implantaat eerst ‘onder het tandvlees begraven’ (d.w.z. het tandvlees

werd teruggehecht over het ingebrachte implantaat)(conventionele groep). Na

drie maanden werd het implantaat ‘opgezocht’ (d.w.z. er werd een verbinding

gemaakt tussen het in de kaak gelegen implantaat en de mondholte) en werd het

implantaat voorzien van een tijdelijke kroon. Drie maanden na plaatsen van de

tijdelijke kroon, werden de implantaten voorzien van een volledige keramische

definitieve kroon. Zes en achttien maanden na plaatsen van het implantaat, kwa-

men de patiënten terug voor nader onderzoek. De primaire uitkomstmaat van

deze studie was peri-implantair marginaal botverlies, gemeten op gestandaardi-

seerd vervaardigde röntgenfoto’s. De uitkomst van direct belasten werd slechter

beschouwd dan conventioneel belasten, als bij direct belaste implantaten gemid-

deld ten minste 0,5 mm meer peri-implantair botverlies optrad. Andere variabe-

len waren implantaat-overleving, aspecten van de peri-implantaire mucosa (poc-

ketdiepte, plaque, bloeding, niveau van de peri-implantaire mucosa), esthetisch

resultaat (gemeten met behulp van PES-WES en ICAI) en patiënttevredenheid.

Alle implantaten hadden een goede primaire stabiliteit (≥ 45 N/cm insertie tor-

sie). Na 18 maanden bleek geen verschil in marginaal peri-implantair botverlies

tussen beide studiegroepen (directe groep 0.91 ± 0.61 mm, conventionele groep

0.90 ± 0.57 mm). Eén implantaat uit de directe groep ging verloren, drie weken

na plaatsing van implantaat en kroon. Er gingen geen implantaten verloren in de

conventionele groep. Tussen beide groepen werden geen verschillen waargeno-

men in pocketdiepte, hoeveelheid plaque, hoeveelheid bloeding en het niveau

van de peri-implantaire mucosa. Ook werd geen verschil in esthetisch resultaat

en patiënttevredenheid gemeten.

Met inachtneming van de beperkingen van deze studie (groepsgrootte en

follow-up), blijkt dat direct belasten van solitaire implantaten in de esthetische

zone niet onderdoet voor conventioneel belasten. Omdat direct belasten voor-

delen biedt voor de patiënt, moet dit concept worden beschouwd als een veel-

belovend alternatief voor conventioneel belasten. Echter, het concept van direct

belasten moet men uitvoeren volgens een specifiek protocol, met aandacht voor

voldoende primaire stabiliteit van het implantaat, een tijdelijke kroon uit occlusie

en goede instructie en medewerking van de patiënt.

In hoofdstuk 6 wordt een casus beschreven waarbij een solitair implantaat

in de esthetische zone direct werd belast met een tijdelijke kroon. Onder an-

dere wordt ingegaan op hoe de tijdelijke kroon werd vervaardigd, hoe deze werd

aangepast en hoe werd zorggedragen voor een optimaal profiel van de tijdelij-

ke kroon. Nadat de tijdelijke kroon zijn functie had vervuld, werd middels een

speciale afdruktechniek het optimale profiel van de tijdelijke kroon overgebracht

naar de definitieve kroon. Deze definitieve kroon was volledig keramisch, kon

rechtstreeks in het implantaat worden geschroefd en bestond uit een volledig

keramische opbouw. Met behulp van dit protocol werd een optimaal esthetisch

eindresultaat verkregen.

In hoofdstuk 7 wordt een casus beschreven van een trauma tegen een kroon

op een implantaat. Door een slag of stoot, kunnen het implantaat, de kroon en

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het peri-implantaire weefsel beschadigd raken. Bij deze casus was de kroon naar

palatinaal verplaatst. Na zorgvuldig onderzoek en follow-up bleek dat enkel de

schroef, waarmee de kroon in het implantaat was gefixeerd, te zijn beschadigd.

De kroon kon gemakkelijk worden teruggeplaatst op het implantaat, en weer wor-

den gefixeerd met een nieuwe schroef.

In hoofdstuk 8 worden de voornaamste onderzoeksresultaten bediscussieerd

en worden conclusies getrokken. Uit dit onderzoek blijkt dat, voor wat betreft een

behandeling met een solitair implantaat in de esthetische zone, een implantaat

met een 1,5 mm gladde hals of met een ruwe hals met groeven, minder peri-

implantair botverlies en betere klinische resultaten vertoont dan een implantaat

met een gewelfde ruwe hals met groeven. Tussen de toegepaste halstypen bleek

echter geen verschil in esthetisch resultaat en patiënttevredenheid. Verder wordt

geconcludeerd dat het direct belasten van een solitair implantaat in de esthe-

tische zone op de korte termijn niet tot een minder gunstig resultaat leidt dan

conventioneel belasten. Vervolgonderzoek moet uitwijzen of deze conclusies ook

gelden voor de lange termijn.

dankwoord Onderzoek verrichten is teamsport. Mede dankzij een team van spelers is dit

proefschrift tot stand gekomen. Ik ben dit team erg dankbaar voor het goede

samenspel. Het waren niet alleen deze spelers, maar ook anderen die een belang-

rijke rol hebben vervuld bij de totstandkoming van dit proefschrift. In de eerste

plaats ben ik alle onderzoekspatiënten veel dank verschuldigd voor hun mede-

werking aan dit onderzoek. Ook dank ik de mensen die langs de zijlijn hebben

gestaan en mij als onmisbare supporters steunden met dit onderzoek. Graag wil

ik een aantal ‘spelers’ en ‘supporters’ persoonlijk bedanken.

Prof. dr. G.M. Raghoebar, hooggeleerde eerste promotor, beste Gerry. Jouw ge-

drevenheid en enthousiasme voor de wetenschap zijn buitengewoon. Jij vormde

samen met Henny en Arjan het trio die de basis legden voor dit proefschrift.

Gerry, ik heb veel bewondering voor jouw klinische talent en jouw vooruitziende

blik voor onderzoeksvraagstukken die de implantologie bezig gaan houden. Ik

ben je dankbaar voor het vertrouwen dat je me hebt gegeven om dit promotie-

traject te doorlopen en voor de tijd die je altijd voor mij wist vrij te maken, ook

voor zaken die naast het werk speelden. Ik vond de manier van samenwerking erg

plezierig en de waardering die je me hebt gegeven, werkte zeer motiverend. Ook

dank ik je voor de mogelijkheid om me naast mijn onderzoek te bekwamen in de

klinische aspecten van de implantologie. Ik heb leuke herinneringen aan onze

contacten buiten het werkveld (zoals de activiteiten bij de NVOI en natuurlijk de

jaarlijkse voetbalwedstrijd tegen de studenten) en hoop in de toekomst op nog

meer mooie herinneringen.

Prof. dr. H.J.A. Meijer, hooggeleerde tweede promotor, beste Henny. Tijdens

mijn afstudeerscriptie, die ik bij jou heb geschreven, wist jij me te enthousias-

meren voor dit promotieonderzoek. Als lid van het ‘spelerstrio’ Gerry, Henny en

Arjan, had jij een onmisbaar aandeel in de totstandkoming van dit proefschrift.

Jouw vermogen om hoofdzaken van bijzaken te onderscheiden verdient veel res-

pect. Samen met Gerry, had jij het ‘Fingerspitzengefühl’ voor de relevantie van

het onderwerp van dit proefschrift. Je was altijd uiterst collegiaal en ik waardeer

de laagdrempelige manier waarop we met elkaar kunnen omgaan. Ik dank je voor

de ervaring die ik onder jouw begeleiding heb opgedaan in de prothetiek op im-

plantaten, maar ook voor het prettige informele contact, zowel op de werkvloer

als daar buiten.

Prof dr. A. Vissink, hooggeleerde derde promotor, beste Arjan. Ook jij was lid

van hét 'spelerstrio' en opereerde in het beginstadium van het onderzoek vooral

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achter de schermen. Daarna werd jouw rol meer zichtbaar en was je van grote

waarde bij het schrijven van dit proefschrift. Jouw capaciteit om binnen zeer korte

tijd artikelen te voorzien van suggesties en kritisch commentaar, grenst aan het

randje van het onvoorstelbare. Je wist met jouw commentaar feilloos de vinger

op pijnlijke plekjes te leggen, waardoor de kwaliteit van dit proefschrift significant

is verbeterd (is niet statistisch getest, maar hoeft ook niet, het is gewoon zo). Ik

dank je verder voor de prettige manier van samenwerken tijdens de spreekuren

en voor het bijbrengen van de chirurgische vaardigheden op het gebied van de

implantologie.

Prof. dr. E. Rompen. I would like to thank you for your willingness to participate

as a member of the PhD-committee and for the time you have spent on judging

the manuscript. Furthermore, I would like to thank you for being a speaker at the

symposium the day before the defence of the thesis.

Prof. dr. G.J. Meijer en prof. dr. D. Wismeijer, hooggeleerde leden van de be-G.J. Meijer en prof. dr. D. Wismeijer, hooggeleerde leden van de be-

oordelingscommissie. Ik wil u graag bedanken voor de bereidheid om zitting te

nemen in de beoordelingscommissie en voor de tijd die u hebt genomen om mijn

manuscript te beoordelen.

Prof. dr. L.G.M. de Bont, geachte professor. Graag bedank ik u voor de gele-

genheid die u mij heeft gegeven om op de afdeling kaakchirurgie dit promotie-

traject te doorlopen. Onder uw leiding heerst er een open en prettige sfeer op de

afdeling en ligt er een solide basis voor onderzoek. Dit heeft zeer wel bijgedragen

tot de voltooiing van dit proefschrift. Ik ben u verder erkentelijk voor de mogelijk-

heid om naast mijn onderzoek de opleiding tot implantoloog te volgen.

Drs. H.J. Santing, beste Eric. Samen zaten we in het bestuur van de Tandheel-

kunde Mondhygiëne Faculteitsvereniging (TMFV Archigenes). Een geweldig jaar!

Gelukkig hebben we de foto’s en de anekdotes nog. Na je afstuderen voegde ook

jij je als onderzoeker bij onze onderzoeksgroep. Op de werkvloer konden we het

goed met elkaar vinden, maar ook op andere vloeren hebben we mooie momen-

ten beleefd. Jammer dat het ‘minibar-moment’ tijdens het jaarlijkse EAO congres

verloren dreigt te gaan. Hopelijk komen hier in de toekomst andere tradities voor

in de plaats. Jij nog veel succes met het afronden van jouw promotietraject. Be-

dankt dat je mijn paranimf wilt zijn.

Dr. N. Tymstra, beste Nynke. Ooit werden we meneer Enkeltands en mevrouw

Dubbeltands genoemd. Wellicht verandert dit straks in Dr. Enkeltands en Dr.

Dubbeltands. Onze promotietrajecten startten tegelijk en kenden veel raakvlak-

ken. We hebben veel samengewerkt en samen gewerkt op de onderzoekskamer

die we jaren deelden. Discussies werden gevoerd over onderzoeksvraagstukken,

maar ook onderwerpen buiten ons onderzoeksveld kwam regelmatig ter sprake.

Hoogtepunten waren de diverse EAO congressen, het gezamenlijk optreden op

Malta en natuurlijk het bezoek aan Las Vegas. Ik vind het erg bijzonder dat we ons

(bijna) gelijktijdig hebben ontwikkeld tot ‘volwaardig onderzoeker’. Ik bedank je

voor de leuke onderzoekstijd die we samen hebben beleefd en voor je kritische

blik op mijn proefschrift. Bedankt dat je mijn paranimf wilt zijn.

Dr. C. Stellingsma, beste Kees. Je fungeerde regelmatig als een belangrijke

mentor. Ik kon met je van gedachten wisselen over onderzoekskwesties en dat

werkte verhelderend. Ik dank je voor je rol als medeauteur en voor het behande-

len van een groot aantal onderzoekspatiënten. Ook dank ik je voor de leuke tijd

op congres. De warme nootjes zal ik niet snel vergeten.

Mw. E. Wartena, beste Esther. De logistiek, planning en assistentie rond een

grote klinische studie is geen sinecure. Alleen het inplannen al van een slordige

1300 afspraken (ongeveer 11 afspraken per onderzoekspatiënt) verdient veel res-

pect, helemaal als de programma’s van de behandelaars al zo vol zitten. Jij kreeg

het voor elkaar en wist het hele onderzoeksproject hiermee te stroomlijnen. Je

leverde elke woensdagochtend maatwerk zodat het meetwerk weer kon beginnen.

Hartelijk dank voor je inzet en de leuke samenwerking.

Dhr. G. van Dijk, beste Gerrit. Graag wil ik je bedanken voor de positieve sa-

menwerking betreft het tandtechnische aspect van dit onderzoek. In jouw tand-

technische laboratorium werden alle kronen vervaardigd samen met een groot

deel van de richtplaatjes, binnen soms praktisch onmogelijke levertijden. Gerrit

en alle medewerkers van het Tandtechnisch Maxillofaciaal Laboratorium Gerrit

van Dijk, hartelijk dank hier voor. Dankzij jullie flexibiliteit, bleek niets te veel

gevraagd.

Dhr. A.K. Wietsma, beste Anne. Ik wil je hartelijk bedanken voor het vervaardi-

gen van de eerste richtplaatjes en je belangrijke bijdrage aan de planning van de

positie van de implantaten. Ook dank ik je voor je bereidheid om immer ad-hoc

in je ‘hok’ met kunstgrepen de zaak te redden (een gebroken plaatprothese, een

zoekgeraakt boorsjabloon, een krom richtstaafje etc.).

Mw. M.A. Bezema, mw. B. Termeulen-Brongers, mw. H.H. Kooistra-Veenkamp,

mw. I.J. Valkema, beste Ans, Bertina, Ria en Ingrid. Hartelijk dank voor jullie on-

dersteuning bij het behandelen van de onderzoekspatiënten en jullie zorgvuldige

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werk achter de schermen. Dankzij jullie resulteert de ‘PPC’ niet in een Pre Pro-

thetische Chaos.

Mw. L.M.E. Kamstra-Dooper, mw. E.J.G. van Luijk-Voshaar, mw. A. van Oploo-

Talens, mw. A. Prins-Schutter, mw. Y. Sanders-Niessen, beste Liliane, Emmy, Tiny,

Anja en Yvonne. Ik dank jullie dat ik altijd mocht inbreken in jullie drukke pro-

gramma voor het maken van de vele röntgenfoto’s voor dit onderzoek.

Prof. dr. B. Stegenga, beste Boudewijn. ‘Het is allemaal niet zo ingewikkeld,

als je maar denkt dat je het kunt’. Hartelijk dank voor deze visie, voor je rol als

medeauteur en voor het boeiende informele contact.

Dr. J.J.R. Huddleston Slater, beste James. Mede dankzij jouw hulp, werd mijn

eerste publicatie een feit. Dat deze publicatie beloond werd met de NVGPT publi-

catieprijs, zie ik als een bekroning op onze samenwerking. Saillant detail is dat ik

deze prijs uit jouw handen mocht ontvangen. Ik dank je verder voor het oplossen

van diverse methodologische en statistische vraagstukken (soms eenvoudig via

‘human eyeball criteria’).

Dr. L. Meijndert, beste Leo. Op de afdeling Kaakchirurgie was jij de pionier op

het terrein van onderzoek naar solitaire implantaten in de esthetische zone. Jij

onthulde de fascinerende aspecten van deze onderzoekslijn en legde een goede

basis voor vervolgonderzoek. Dank voor het gespreide bedje dat je voor me klaar

hebt gezet.

Drs. G. Telleman, drs. J.W.A. Slot, drs. K.W. Slagter, drs D. Rickert en drs. Y.C.M.

de Waal, beste Gerdien, Wim, Kirsten, Daniela en Yvonne. Hartelijk dank voor jul-

lie interesse in mijn onderzoek en het goede gezelschap tijdens de congressen.

Veel succes met het afronden van jullie promotieonderzoek.

Mw. N.E. Jaeger, mw. L. Kempers, mw. K. Wolthuis, dhr. P. Haanstra, dhr. H.B.

de Jonge en dhr. R.M. Rolvink, beste Nienke, Lisa, Karin, Piet, Harry en Richard.

Bedankt voor jullie secretariële, technische en faciliterende ondersteuning.

Alle mede-onderzoekers en AIO’s van de afdeling Kaakchirurgie. Hartelijk dank

voor jullie belangstelling en de leuke contacten rond de diverse koffieautomaten

en aan de lunchtafels.

Alle niet met name genoemde medewerkers van de afdeling Kaakchirurgie.

Hartelijk dank voor de plezierige samenwerking.

Alle medewerkers van Tandartsenpraktijk Loppersum. Heel veel dank dat ik –

naast mijn onderzoek – altijd onbezorgd hier kon werken. Altijd was alles perfect

geregeld en kon ik na een dag(deel) werken weer rustig verder met mijn onder-

zoek. Ook waren mijn patiënten tijdens mijn afwezigheid altijd in goede handen.

Ab en alle medewerkers van dé praktijk, er is geen betere praktijk denkbaar om te

mogen werken.

Lieve broer, zusje, opa, Jeltje en schoonfamilie. Hartelijk dank voor jullie war-

me belangstelling en steun. Jullie waren onmisbaar als ‘twaalfde man’. Opa, wat

speciaal dat u de verdediging van mijn proefschrift gaat meemaken. Willemijn, jij

in het bijzonder bedankt voor de gevulde Tupperwarebakjes voor als er thuis weer

geen tijd was om te koken.

Lieve ouders. Jullie hebben mij altijd gesteund en mij vrij gelaten in het maken

van mijn keuzes. Ik ben jullie dankbaar voor de solide thuisbasis en het feit dat ik

altijd op jullie kan rekenen. Zonder jullie was ik nooit zo ver gekomen. Heel veel

dank hier voor!

Lieve Femke. Jij was mijn belangrijkste supporter en mijn steun en toeverlaat

als het even tegen zat. Dat jij bezig bent met het afronden van je tweede studie

werkte zeer motiverend. Samen sluiten we straks een drukke periode af. Dat we in

deze periode echt naar elkaar zijn toegegroeid, betekent gewoon dat wij bij elkaar

horen. We vormen het perfecte duo en vullen elkaar zó goed aan. Sorry, dat ik de

laatste tijd misschien wat afwezig ben geweest (‘je luistert niet!’…. ‘euhh…wat zeg

je?’), maar dit maak ik straks weer meer dan goed! Lieve Femke, jij bent de reden

dat ik na mijn werk weer zin heb om naar huis te gaan. Over een paar maanden

zeg ik zonder enige twijfel ‘ja’ tegen jou. Je bent mijn topper. Ik hou van je!

160

Curriculum VitaeLaurens den Hartog was born on 9 September 1980 in Steenwijk, the Net-

herlands. After finishing secondary school, he studied dentistry at the Uni-

versity of Groningen. During his study, he was chairman of the student

faculty association of dentistry and was an employee of the Central Medical

Library. He graduated as a dentist in 2004 and combined the PhD research

described in this thesis with his work as a dentist in a private practice in

Loppersum. Furthermore, Laurens worked as a dentist and as a teacher in

implant prosthodontics at the Dental School of the University of Gronin-

gen. In 2010 he finished a post-doc training program to become an implan-

tologist. Currently, he is secretary of the board of the Dutch Society of Oral

Implantology (NVOI).

L. den Hartog

University Medical Center Groningen

Department of Oral and Maxillofacial surgery

9700 RB Groningen

The Netherlands

[email protected]

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