The “hybrid abutment”: a new design for implant cemented ... · Recently, a prosthetic...

CLINICAL RESEARCH

186THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

Correspondence to: Dr Roberto Cocchetto, MD DDS

Via Albere 10, 37138, Verona, Italy; E-mail: [email protected]

The “hybrid abutment”:

a new design for implant cemented

restorations in the esthetic zones

Roberto Cocchetto, MD, DDS

Independent Researcher, Private Practice, Verona, Italy

Luigi Canullo, DDS

Independent Researcher, Private Practice, Rome, Italy

COCCHETTO/CANULLO


Abstract

Cemented implant restorations are wide-

ly used by many dentists. The tradition-

al abutment design resembles a natural

tooth prepared for a crown with a similar

taper and a chamfer finish line. A fre-

quent complication associated with im-

plant restorations in the esthetic zones

is the recession of buccal gingiva over

time. Abutment morphology, among

several other prosthetic factors, may

play an important role in the stability of

the gingival margin in esthetically sensi-

tive areas, but this has never been thor-

oughly analyzed. Recently, a prosthetic

technique called biologically oriented

preparation technique (BOPT) has been

proposed, which utilizes a feather-edge

preparation on natural abutments, and it

has been claimed that applying the con-

cepts of this technique to implant abut-

ments could improve long-term gingival

margin stability. At present, there is no

available evidence to confirm this claim.

Moreover, some concerns may arise if

this particular design is implemented in

every clinical situation. With these con-

siderations in mind, this article proposes

the “hybrid abutment” design (HAD), a

new design that includes a combination

of the two types of features – a feather

edge on the buccal side, and a chamfer

finish line on the lingual side. The article

also presents a rationale for the use of

different abutment designs for different

situations.

(Int J Esthet Dent 2015;10:186–208)


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Introduction

The restorative protocols for implant-

supported restorations have changed

significantly since the original protocols

proposed for the treatment of fully eden-

tulous mandibles,1 and later for partially

edentulous sites. The connection be-

tween the prosthetic crown and the im-

plant was strictly screw-retained, with the

interposition of a transmucosal titanium

abutment, either straight or angulated,

depending on the axial divergence be-

tween the implant and the crown. Later,

a direct connection of the crown to the

implant platform was introduced,3,4 and

the cement-retained modality of restor-

ation became widely used. In this mo-

dality – which is similar to the method for

restoring a natural tooth – the abutment,

either prefabricated or customized, is

connected to the implant by a retaining

screw (some systems use a solid abut-

ment, press-fitted or cemented into the

implant body), and the crown cemented

onto it.

Technically, implant abutments can

be produced in several ways:

a) Prefabricated in some basic designs,

usually straight or angulated, and then

modified intraorally by the dentist (direct

procedure) or in the laboratory by the

dental technician on the working cast

(indirect procedure).

b) Customized though a wax-up of a

gold cylinder and cast with a metal no-

ble alloy. This modality is less commonly

used nowadays.

c) Digitally designed (or scanned from a

wax or resin matrix) and milled in a CAD/

CAM process.

The abutment morphology traditionally

mimics a prepared natural abutment,

with an axial wall convergence angle

6 depend-

ing on the different authors’ preferences.

The intrasulcular part of the abutment

emerges from the implant platform, ex-

panding coronally to reach the buccolin-

gual and mesiodistal dimensions of the

prosthetic tooth to be replaced (Fig 1).

The emergence profile of the abutment

is continued into the emergence profile

of the crown, and a defined finish line

(usually a chamfer) is placed on the

abutment and generally positioned sub-

gingivally on the buccal (“esthetic”) side.

Therefore, the buccal gingival contour is

“shaped” by the abutment profile. The

finish line is important for the verification

of the crown’s margin adaptation during

the try-in session and after cementation.

Moreover, it acts as a vertical stop for the

distribution of functional loads.

Fig 1 Traditional chamfer abutment design.

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This traditional margin design has two

main drawbacks:

a) The geometry of the finish line implies

that the greater the angle of the shoulder

(up to 90 degrees), the larger the mar-

ginal discrepancy after crown cementa-

tion. It has been suggested that this gap,

which is colonized by bacteria, may be

an important factor in buccogingival re-

cession over time.7

b) The emergence profiles tend to

“push” the peri-implant buccal soft tis-

sue outward and in the apical direction.

This can be easily observed, for exam-

ple, when changing a healing abutment

connected to an implant with a larger

one that has a more divergent profile. It

will be noticed that, after a short time, the

vertical level of the gingival margin will

recede in the apical direction, and the

thickness of the buccal gingiva will be

reduced. Reversing the procedure and

connecting a straight (or even conical)

abutment will determine a coronal repo-

sitioning of the gingival margin.

All other variables being equal, the com-

bination of the above two factors (mar-

ginal gap and expanded profile) may

explain the higher incidence of buccal

gingival recession in cemented implant

restorations in the esthetic zones8-14

morphology of the abutment that could

improve these two aspects have been

considered.

Recently, a prosthetic restorative pro-

cedure called the biologically oriented

preparation technique (BOPT) has

been described in the literature. In

this technique, the feather-edge prep-

aration originally developed for peri-

odontal prostheses is also applied

Fig 2 Gingival recession displaying metal abut-

ment neck.

Fig 3 (a) Gingival asymmetry in the esthetic zone is also visible when the patient is not smiling. (b) Sym-

metric parabolic architecture, prosthetically generated. (c) Completed case.

a b c

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Fig 4 Correct marginal design for feather-edge

restorations.

Fig 5 The shoulderless abutment design.

to periodontally healthy teeth with the

purpose of eliminating the horizontal

component of an unprepared tooth (or

any pre-existing finish line in an already

prepared tooth), allowing the formation

of a new “prosthetic” cement –enamel

junction. This allows the creation of ideal

esthetic contours of the crown, to which

the gingiva adapts without the need for

surgical intervention (Figs 3a to 3c).

It has been claimed that this technique

offers several advantages, a major one

being a better marginal adaptation of the

crown after cementation and a minimal

microgap compared to traditional “hori-

zontal” preparations, such as chamfer or

shoulders. Moreover, the crown’s emer-

gence profile supports and shapes the

buccal soft tissue, which adapts itself

to the tooth contour. The clinical con-

sequences of this simple observation,

which questions the traditional definition

of prosthetic “overcontour”, are relevant:

the gingival portion of the crown, in fact,

can be designed as desired, being freed

from the geometric limitation of the abut-

ment’s margin line. As a consequence,

increased stability of the gingival margin

over time should be expected, with little

or no buccal gingival recession.

The technical criticism of the weak-

ness of the feather-edge margin of the

crown in supporting the occlusal

stress is overcome by designing a re-

inforced “strength collar”, either for por-

celain fused to metal (PFM) or metal-free

(zirconia) frameworks (Fig 4).

Similar restorative concepts have also

been suggested for the implant abut-

ment design, and have been applied

by the authors in a case series, mostly

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clinical results in terms of buccal gin-

gival margin stability, compared to the

more frequently experienced recession

with the shoulder/chamfer design.

The principal reasons for these posi-

tive results are:

a) The minimal post-cementation gap

(similar to what happens in natural teeth,

as previously mentioned).

b) The elimination of the horizontal com-

ponent of the traditionally designed

shoulder abutment, which leaves a wid-

er available space for soft tissue thick-

ening (Figs 6a to 7b).

All other variables being equal (bone

volume, gingival biotype, correct im-

plant size and position, soft tissue en-

hancement), it seems that a shoulder-

less abutment and the corresponding

crown margin may offer a better chance

for the health and stability of the gingival

margin. Even if clinical studies are need-

ed to confirm this hypothesis, there is

Fig 6 (a and b) Chamfer abutments and thin buccal tissue.

Fig 7 (a and b) Shoulderless abutments and increased buccal tissue thickness.

a b

a b

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consistent clinical evidence supporting

the application of this design for implant

abutments.

However, some critical considera-

tions must be borne in mind regarding

the implementation of the feather-edge

abutment in every case:

The lack of a finish line could make

it more difficult to control the fit of the

crown, especially when multiple im-

plants are splinted for mechanical

reasons or simply as part of a cement-

ed implant bridge.

With the shoulderless abutment, the

walls’ convergence angle tends to be

reduced toward 0 degrees; otherwise,

due to the presence of the internal

screw access hole, a more tapered

preparation would eliminate much of

the retentive surface of the abutment.

The retrievability of the crown is there-

fore almost impossible, even if tem-

porary cement is used.

Another common criticism of the

feather-edge abutment design is the

possible increased risk of undetected

excess cement in peri-implant soft tis-

sues. This complication seems to oc-

cur more frequently than expected in

cemented implant restorations, in par-

ticular when a resin cement is used.

A greater risk of peri-implant disease

was found in periodontally compro-

mised patients with cemented implant

restorations when excess cement re-

mained undetected in the peri-implant

sulcus. Moreover, a positive cor-

relation was found between a deeper

subgingival margin and the amount of

undetected cement.

In the authors’ opinion, the use of a

shoulderless abutment design (Fig 8)

may further increase the risk of resid-

ual excess cement, such as in molar

teeth, where the difference in diameter

between the implant platform and the

crown (undercut) could lead to an in-

accessible subgingival margin and to

the persistence of undetected cement

Fig 8 Shoulderless abutment in a posterior tooth.

Fig 9 (a) Radiological cement remnants may

only be visible interproximally. (b) Buccal cement

remnants are only detectable if the crown can be

retrieved.

a b

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remnants with possible marginal bone

loss (Figs 9a and 9b). For these rea-

sons, a modified abutment is proposed

which incorporates features of the two

previously mentioned designs.

The hybrid abutment

design (HAD)

There are three distinct zones in the HAD

design (Fig 10):

a) The buccal zone: This portion (Figs 11

-

nent. It resembles the buccal side of a

natural tooth prepared with no finish line,

and will receive the feather-edge margin

of the crown. Therefore, the post-cemen-

tation gap will be minimal compared to a

shoulder design. The crown margin will

be positioned slightly subgingivally, be-

-

plete removal of excess cement. The

crown emergence profile supports and

shapes the gingival margin and can be

contoured based on esthetic needs. The

clinical advantage offered by the shoul-

derless design to maintain the buccal

soft tissue margin indicates this design

for esthetic zones.

b) The linguopalatal wall: This portion

chamfer finish line that is located su-

pragingivally or at the gingival level, if

necessary, to increase retention in case

of short abutments. For the same rea-

son, one or two retaining grooves can

be added in the palatal wall. The acces-

sible margin is an important reference

point when inspecting the crown’s seat-

ing, and the horizontal component of

the chamfer helps to dissipate occlusal

stress. No subgingival cement is ex-

pected in this area. The lack of esthetic

relevance of this portion indicates the

shouldered design.

c) The interproximal walls: In this por-

toward the interproximal surfaces of

the smooth walls, with no horizontal

Fig 10 The hybrid abutment design.

Fig 11 The hybrid abutment: buccal view.

Fig 12 The hybrid abutment: interproximal view.

Fig 13 The hybrid abutment: palatal view.

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component. Regarding the buccal wall,

the soft tissue of the papillae. Depend-

ing on the soft tissue levels, the intrasul-

cular portion of the restoration is freely

designed to maintain optimal esthetic

contour and gingival health.

Clinical indications for

different abutment designs

Posterior quadrants

(1) When the edentulous area has a good

soft tissue quality with an adequate di-

mension of keratinized gingiva (≥ 3 mm),

a traditional abutment design with a defi-

nite margin can be used (Fig 14). Better

control of the marginal adaptation of the

restoration is facilitated, as well as the

complete removal of excess cement.

This situation is illustrated, for exam-

ple, by a mandibular posterior edentu-

premolar and the first molar were to

be replaced by two implant-supported

crowns. A single-stage surgery was per-

implant in the molar area, a 4 mm heal-

ing abutment was placed in order to start

a platform-switching restorative pro-

cedure (Fig 17), which has been dem-

onstrated to be effective in peri-implant

bone preservation.

An impression was taken after 8

weeks, and two abutments were pre-

pared on the sectioned master cast

Fig 14 Chamfer abutment in a posterior tooth.

Fig 15 Posterior edentulous ridge.

Fig 16 Two implants healed after a single-stage surgery.

Fig 17

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from a commercial titanium component

(Tissuemax, Biomax) (Fig 18). The abut-

ments were designed with a chamfer fin-

ish line, only slightly subgingival on the

buccal side, and were duplicated on the

master cast using the abutment dupli-

cation technique (ADT) technical pro-

tocol30 (Fig 19), then digitally scanned

with the Sirona InEos Blue laboratory

-

ary acrylic crown milled from the digi-

-

ed at the time of abutment connection

After two months, on the same data-

set, the final ceramic on zirconia res-

torations were completed onto the ADT

-

ther impression. The temporary crowns

-

torations were cemented with TempBond

-

tion was made during the entire restora-

tive protocol, which followed the “one

abutment/one time” concept designed

by the authors as part of a minimally in-

vasive prosthetic protocol that has been

proven to reduce peri-implant marginal

bone loss.31 At the 3-year follow-up,

the excellent hard and soft tissue levels

Fig 18 Titanium abutments prepared with a circumferential chamfer finish line.

Fig 19 Replicas on the original working model of the polyurethane abutments.

Fig 20 Scan view of the original metal abutments.

Fig 21 Digitally designed temporary crowns.

Fig 22 PMMA (polymethylmetacrylate) crowns, milled.

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(2) When the edentulous area has a

poor soft tissue quality and volume, with

a band of keratinized gingiva of < 3 mm,

the shoulderless abutment design is

Fig 23 Abutments and crowns

in place.

Fig 24 Radiographic control.

Fig 25 Zirconia/ceramic crowns completed on duplicate abutments.

Fig 26 Temporary crowns are removed.

Fig 27 Final restorations are cemented.

Fig 28 Radiographic control after 3 years of func-

tion.

Fig 29 Clinical image at 3-year control.

indicated more frequently if a buccal

subgingival margin is planned in cases

where patients demonstrate particular

esthetic demands.

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Fig 34 Titanium hybrid abutments: buccal view.

Fig 35 Titanium hybrid abutments: lingual view.

Fig 30 Two implants placed in the posterior mandible.

Fig 31 The band of keratinized tissue is very limited but healthy.

Fig 32 Healing abutments are removed for pick-up impression.

In this case (2), the situation differs

from that described above (1) as re-

gards the limited amount of buccal soft

tissue. Moreover, the implant platform is

placed at crestal level (Figs 30 and 31),

and therefore the transmucosal compo-

nent of the abutment profile is minimal,

except for the mesial side of the first im-

is indicated to combine precision with

an “esthetic” buccal margin with no fin-

ish line (Fig 34). The lingual chamfered

-

ment-retained surface and an adequate

taper to allow retrievability. The abutment

duplication and the digital prosthetic

process (Figs 36 to 38) are the same

as in the preceding case (1), from abut-

ment connection (Figs 39a and 39b) to

temporization (Fig 40). Again, no further

abutment disconnection is made, and

the case is finalized without the need of

Fig 33 A hybrid abutment design was chosen.

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Fig 36 Scan view of the abutments.

Fig 37 The profiles of the crowns are designed for both temporary and final restorations.

Fig 38 PMMA milled crowns before delivery.

Fig 39 (a) Single and final connection of the abutments. (b) Radiographic control.

Fig 40 Temporary crowns are cemented.

Fig 41 Zirconia/ceramic crowns completed on

duplicated abutments.

Fig 42 Final restorations in place.

a b

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Esthetic zones

The primary indication for the HAD is

the esthetic zone of the maxillary arch,

which, depending on the smile line and

the relative display of the buccal gingi-

val margins, may extend back to the first

molars, especially in “gummy” smiles.

In the following clinical case, the hope-

less central left incisor was planned

for extraction and replacement with an

implant-supported crown (Figs 43 and

44). The solution requested by the pa-

tient to the diastema problem involved

the implementation of a veneer ceramic

restoration on the contralateral incisor,

-

cession was also present. At the time of

extraction, a socket preservation tech-

-

lowed by a delayed implantation and

delayed loading.

Fig 45 Socket is grafted with osteoconductive

material.

Fig 46 A Leukocyte-Platelet Rich Fibrin (L-PRF)

membrane is used to seal the socket.

Fig 43 Hopeless left central incisor planned to be extracted.

Fig 44 Severe periodontal lesion is also documented by radiograph.

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After 3 months, an implant-level im-

pression was taken (Figs 47a and 47b),

and a resin matrix of the abutment with

hybrid features was prepared (Fig 48),

scanned, and milled in the laboratory in

titanium (Fig 49), together with the digi-

tally designed and milled polymethyl-

metacrylate (PMMA) crown and the zir-

conia framework for the final restoration

edge buccal margin and a chamfer lin-

gual margin, and exactly the same emer-

gence profile. Note how the “strength

collar” has an intrasulcular component

with a maximum of 1 mm, which ensures

the complete removal of excess cement.

Fig 47 (a) Healing at 3 months, after a delayed implant placement and osseointegration. (b) Coping in

place for pick-up impression.

Fig 48 A resin framework abutment is built for scanning.

Fig 49 Titanium-milled hybrid abutment is produced and duplicated.

a b

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Fig 54 After 6 weeks, soft tissues are shaped by the crown’s profile.

Fig 55 Veneer preparation on right incisor, ready for impression, together with zirconia framework on left

incisor hybrid abutment.

Fig 50 (a) The crown is digitally designed. (b) Temporary PMMA crown is produced by milling. (c) Final

zirconia framework is also milled.

Fig 51 Abutment connection.

Fig 52 Temporary crown cemented.


a b c

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and the acrylic crown cemented, while

an interim composite restoration was

applied to match the contralateral inter-

proximal contour and to close the dias-

After 6 weeks, the right central inci-

sor was prepared for a ceramic veneer

was taken, incorporating the zirconia

framework for the implant restoration

Fig 56 Impression incorporating the zirconia

framework.

Fig 57 (a) Abutment replica ready for the extraoral cementation procedure. (b) Eugenol-free zinc oxide

cement is mixed and applied into the crown. (c) The crown is placed firmly on the abutment replica and

immediately removed. (d) Excess cement is wiped out of the crown margin, and this is placed intraorally.

(e) The abutment replica is then cleaned and stored in the clinic.

a b

c d e

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In the final clinical session, the veneer

was bonded on the left incisor and the

finalized ceramic zirconia restoration

was cemented on the implant abutment.

A temporary cement was used for this

procedure to maintain the retrievability

of the restoration and reduce the risk of

leaving remnants of excess cement in

the peri-implant sulcus. Moreover, a

controlled cementation technique, more

effective for eliminating the residual ex-

cess cement, was applied. In the

original technique, a silicon putty replica

of the abutment is prepared. The crown

is then filled with cement and placed

onto the replica. The excess cement is

extruded and removed from the crown,

which is immediately positioned on the

abutment intraorally. In the authors’ pro-

tocol, the abutment replica in polyu-

rethane resin, which is more precise,

in the peri-implant sulcus, thanks to the

cementation procedure and also to the

peculiar abutment design, which mini-

mizes the intrasulcular component of the

restoration.

Fig 60

Fig 58 Final restorations after cementation.


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Discussion

The achievement of a long-term esthetic

result in implant-supported anterior res-

torations depends on the combination

of several conditions, among which an

adequate hard and soft tissue volume at

implant site and precise tridimensional

implant placement are of paramount im-

portance. If these factors are not cor-

rectly implemented, very little can be

done through the restorative procedures

alone to improve the poor esthetic result.

These restorative procedures – eg,

implant-level impression, extended use

of temporary abutments and crowns

to progressively shape the soft tissue

architecture, transmucosal customiza-

tions of the final impression coping, final

abutment, crown try-ins – are often very

complex and time-consuming, espe-

cially in cemented prostheses. All these

procedures involve multiple discon-

nection at implant level, with a possible

detrimental effect on peri-implant tissue

stability.36 For this reason, the simplifica-

tion of the procedures for cemented res-

torations based on the “one abutment/

one time” concept, which is shown in

all of the three cases presented in this

article, may be of significant value, from

both a biologic and a practical perspec-

tive.

Cemented implant restorations, al-

though widely used, present some com-

plications,37 the most frequent being the

loosening of the abutment screw. The

next three most frequent complications

are related to the cemented retention

mechanism: a) loss of retention; b) its

opposite, difficult retrievability; and c) residual intrasulcular cement. The abut-

ment morphology is involved in all of

them, but all its aspects have not been

thoroughly analyzed.

Loss of retention has been advocated

as a reason for the use of permanent or

semi-permanent cements (resin-based

cements, zinc phosphate, glass iono-

mer, polycarboxylate) instead of “tem-

porary” cements (calcium hydroxide,

zinc oxide), the performance of which is

considered “very unpredictable”. This

may not be true if an adequate taper is

used.6 Moreover, altering the abutment

surface through airborne-particle abra-

sion can enhance retention, reducing

the need for a permanent cement.38

The opposite protocol must be used

if a retrievable cemented restoration

is preferred (increase taper, smooth-

er surface), and a balance should be

achieved between insufficient retention

of the prosthesis and retrievability, which

is an advantage for many reasons (re-

pair, cleaning, etc).39 Another important

reason for the use of a temporary ce-

ment is the better radiological identifica-

tion of zinc-based cements compared

to permanent ones,30-33 which helps to

detect intrasulcular remnants, at least

interproximally.

Surprisingly, in the vast body of avail-

able literature on implants and esthetics,

there are few articles about the abutment

morphology as a possible contributing

factor when solving the problem of buc-

cal gingival recession. Although several

articles deal with this problem, most of

them are unclear about the restorative

aspects of the treatment.

The feather-edge abutment has

shown positive effects in terms of gingi-

val margin stability due to the reduced

post-cementation gap geometrically as-

sociated with this design, and also due

COCCHETTO/CANULLO


to the effective thickening of the buc-

cal gingival tissue. This has yet to be

confirmed by clinical studies. Yet, irre-

spective of the kind of design, the risk of

cement remnants in the peri-implant sul-

and eventual mucosal and peri-implant

disease, must be seriously considered.

However, with a feather-edge design,

the subgingivally reversed emergence

profile (coronally convergent) is far more

accessible for cement removal than with

a traditional shoulder design (coronally

divergent). With the latter, when the mar-

gin is placed subgingivally, excess ce-

ment may be trapped beyond and be-

low the abutment finish line. In fact, all

the articles in the literature about the role

of excess cement in peri-implant dis-

ease are based on clinical observations

where the traditional shoulder design

was used. While one study claims

that a particular abutment morphology

with a concave neck9 increases the soft

tissue thickness above the implant plat-

form, two other studies fail to confirm this

claim.40,41 Moreover, the shoulder mar-

gin is still present in this design, which,

in the authors’ opinion, is a fundamental

difference in soft tissue behavior.

Intrasulcular cement excess can also

be a problem with the marginless design

in some situations where the margins

may end up restoring regular implant di-

ameters with large diameter crowns, like

in the molar areas. Therefore, it seems

reasonable to use the traditional shoul-

der design in non-esthetic zones and

keep the margin above the gingiva or at

a minimal intrasulcular depth. However,

public awareness is growing concerning

the possible display of unesthetic metal

margins, even in areas that are not nor-

mally visible. For this reason, the mar-

gin of the crown is more frequently pos-

itioned by clinicians within the gingival

sulcus, including in nonesthetic zones.

The features of the HAD combine a lim-

of the margin on the shoulderless buccal

side with a precise reference point of a

chamfer finish line on the non-esthetic

side of the cemented restoration. This

design is indicated only in esthetic areas

of the mouth, where it might result in pos-

itive clinical effects while, together with

the use of a temporary cement and a

controlled cementation protocol, reduce

the risk of residual undetected cement in

the peri-implant sulcus.

Finally, the use of titanium abutments

needs to be considered. In the present

study, the specific use of titanium as the

material of choice was intended to defy

the “conventional” opinion that titanium

abutments cannot be used in the esthet-

ic zone and that only zirconia should be

allowed. On the contrary, in our clinical

practice we have treated only a few cas-

es with zirconia abutments, those be-

ing patients with scalloped, thin buccal

gingiva. The “consensus” about using

only zirconia in the esthetic zones is not

supported scientifically; nevertheless,

it has become a habit to do so, prob-

ably because there has been no pos-

sible alternative. It should be borne in

mind that zirconia abutments also have

certain drawbacks that are very well

known in clinical practice. If the zirco-

nia abutment is completely metal-free,

the connector part is less precise and

is not strong enough to ensure long-

term performance. On the other hand,

a metallic connector glued to a zirconia

post makes disconnection between the

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components likely. This failure is due to

it being mechanically weaker compared

to a full titanium abutment. The authors’

intention in this article has been to open

a discussion on this topic by propos-

ing a possible alternative, ie, the hybrid

abutment.

Conclusions

Cemented implant-supported restor-

ations are still widely used in the treat-

ment of edentulous sites. The commonly

used abutment design with a definite

finish line poses some problems when

an intrasulcular crown margin is indi-

cated for esthetic reasons. One major

complication is the gingival recession at

the buccal margin. There is some evi-

dence in the literature that a shoulder-

less, feather-edge abutment design in

fixed dental restorations could improve

soft tissue stability over time. While

the assumption that these positive re-

sults may be transferred to the implant

abutment is presently not supported by

published data, the assumption is sup-

ported by the long-term clinical results

obtained by a group of experienced clin-

icians. Moreover, a generalized applica-

tion of this design may raise some con-

cern about the possibility of intrasulcular

cement remnants. The hybrid abutment

– a variation of the shoulderless design

– is proposed, in which a chamfer mar-

gin is maintained on the palatal side and

the intrasulcular component of the res-

toration is limited only to the buccal (“es-

thetic”) side, practically combining the

clinical advantages of the two designs.

underway in order to evaluate the clinic-

al outcome of this specific design.

Acknowledgment

This article is dedicated to the memory of Dr Giam-

paolo Vincenzi, gifted surgeon and great friend.

COCCHETTO/CANULLO


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