Review Article

Rehabilitation of occlusion – science or art?

K. KOYANO, Y. TSUKIYAMA & R. KUWATSURU Section of Implant and Rehabilitative Dentistry, Division of

Oral Rehabilitation, Faculty of Dental Science, Kyushu University, Fukuoka, Japan

SUMMARY The primary objective of rehabilitating

occlusion is to improve stomatognathic function in

patients experiencing dysfunction in mastication,

speech, and swallowing as a consequence of tooth

loss. The procedure of occlusal treatment involves

improving the morphology and the stomatognathic

function. Several practical methods and morpholog-

ical endpoints have been described in occlusal reha-

bilitation. We made a selection of these (mandibular

position, occlusal plane, occlusal guidance, occlusal

contact, face-bow transfer, use of an adjustable

articulator and occlusal support) and performed a

literature review to verify the existence of compel-

ling scientific evidence for each of these. A literature

search was conducted using Medline ⁄ PubMed in

March 2011. Over 400 abstracts were reviewed, and

more than 50 manuscripts selected. An additional

hand search was also conducted. Of the many

studies investigating stomatognathic function in

relation to specific occlusal schemes, most studies

were poorly designed and of low quality, thus

yielding ambiguous results. Overall, there is no

scientific evidence that supports any specific

occlusal scheme being superior to others in terms

of improving stomatognathic function, nor that

sophisticated methods are superior to simpler ones

in terms of clinical outcomes. However, it is obvious

that the art of occlusal rehabilitation requires accu-

rate, reproducible, easy and quick procedures to

reduce unnecessary technical failures and ⁄ or the

requirement for compensatory adjustments. There-

fore, despite the lack of scientific evidence for

specific treatments, the acquisition of these general

skills by dentists and attaining profound knowledge

and skills in postgraduate training will be necessary

for specialists in charge of complicated cases.

KEYWORDS: occlusion, rehabilitation, clinical evi-

dence, technique, skill

Accepted for publication 17 February 2012

Introduction

Dentists aim to rehabilitate occlusion in patients for a

variety of reasons including extreme reduction in the

vertical dimension of occlusion owing to severe dental

wear and severe aesthetic ⁄ phonetic disturbance result-

ing from maxillary resection to aid tumour removal.

Aesthetics is especially important when the maxillary

anterior region is to be rehabilitated. In most cases,

however, the primary objective of occlusal rehabilita-

tion is to improve the stomatognathic function of

patients who have dysfunction or disability in mastica-

tion, speech or swallowing because of either tooth loss

or other reasons. We can currently only provide

treatments to improve morphology (e.g. fabricating

prostheses based on morphological requirements) and

consequently intend to improve stomatognathic func-

tion. A method of occlusal rehabilitation that certainly

improves function is not yet available. These ‘indirect’

methods, that is, improving function by providing an

appropriate morphology, are nevertheless superior to

other prostheses, such as eye prostheses, that are

morphologically correct and have adequate aesthetics

but cannot improve function (e.g. vision).

The assumption that improved stomatognathic func-

tion can be achieved by providing good morphology is

logical only if there is a close positive relationship

between morphology and function such that good

morphology can produce and maintain better function.

Hence, several questions need to be answered. First,Based on a presentation at CORE China 2011.

ª 2012 Blackwell Publishing Ltd doi: 10.1111/j.1365-2842.2012.02303.x

Journal of Oral Rehabilitation 2012 39; 513–521

J o u r n a l o f Oral Rehabilitation

can we improve function and ⁄ or reduce disability by

providing good morphology? Second, can we prevent

deterioration of function by correcting morphology?

Finally, can we prove causality in the above-described

issues?

As an example, the relationship between temporo-

mandibular disorders (TMD) and occlusion has been

discussed for many years. One major concept among

the early aetiologic theories for TMD was the suggestion

that abnormal occlusal contacts were causal factors (1–

4). Extensive studies including systematic reviews have

revealed that there is no strong relationship between

occlusal problems and TMD as previously believed.

There is no strong evidence to support the superiority of

occlusal treatment over any other treatment modalities

(e.g. cognitive behavioural, pharmacological or physical

therapies) nor that providing a ‘good’ occlusion can

prevent the occurrence of TMD (5, 6).

Another example is the link between bruxism and

occlusion. The three main classes of factors causing

sleep bruxism are neurological, peripheral (e.g. occlu-

sion) and psychogenic, of which occlusal problems

were considered the major aetiological factor (7).

Although the aetiology and neurological mechanisms

that generate sleep bruxism are not exactly understood,

a number of studies have proven that central factors

play a major role in its development (8–12), which

appears to be induced within the central nervous

system (9, 13). Moreover, several studies showed that

altered inputs from peripheral oral receptors resulting

from realignment of occlusal contacts or increased

occlusal vertical dimension temporarily diminishes,

but does not stop, bruxism (14, 15). In a randomised

controlled crossover clinical trial, in which the effect of

stabilisation splints and palatal splints (which have zero

coverage of the occlusal surfaces) on sleep bruxism was

examined, both splint designs significantly reduced

sleep bruxism, but the effect was only transient (16).

Also, a double-blind, parallel, controlled, randomised

clinical trial revealed that stabilisation splints were not

efficient in reducing sleep bruxism in a 4-week obser-

vation period (17). It is suggested that changing occlusal

contacts with occlusal splints may not be a primary

factor in reducing sleep bruxism activity. To date, the

accumulated evidence looks neither convincing nor

powerful enough to state conclusively that occlusal

treatment prevents sleep bruxism, and occlusal therapy

is therefore not recommended as a primary method for

managing this condition.

Finally, regarding occlusal rehabilitation as a means

of re-establishing occlusal contacts, studies have

reported functional improvement following restoration

of occlusal contacts between post-canine teeth (18, 19).

The objective masticatory function (chewing perfor-

mance) was significantly improved by the insertion of

removable partial dentures or fixed prostheses in 15

patients who had missing post-canine teeth (18). It is

also reported that masticatory performance signifi-

cantly increased after the insertion of an implant

prosthesis in the second molar region (19). However,

considerable variation was found in the perceived

disability in individuals with missing teeth (20, 21),

and discrepancy between objective and subjective

measures of oral functional improvement was reported

(18). The following section addresses these issues in

more detail.

Morphological goals of occlusal treatment

Several theoretical ⁄ morphological goals for occlusal

treatment can be drawn from dental literature. These

include mandibular position, occlusal plane, occlusal

guidance, occlusal contact, face-bow transfer, use of an

adjustable articulator and occlusal support (22, 23).

Most of these are based on the theoretical concept of an

‘ideal’ occlusion, which is rarely found in the natural

dentition (24).

We performed a literature review to examine the

existence and strength of scientific evidence for each of

these morphological goals of occlusion (Table 1). A

search of the English-language literature was con-

ducted using Medline ⁄ PubMed in March 2011. Search

terms and MEDLINE Medical Subject Headings for the

search included ‘occlusion (dental occlusion)’ and

‘rehabilitation’, with various combinations of these

terms with ‘mandibular position’, ‘intercuspal position’,

‘centric occlusion’, ‘centric relation’, ‘occlusal plane’,

‘inclination’, ‘curvature’, ‘guidance (occlusal guidance

and anterior guidance)’, ‘occlusal contact’, ‘artificial

tooth ⁄ teeth’, ‘face-bow or facebow’, ‘articulator (dental

articulators)’ and ‘occlusal support’. Abstracts of the

following types of articles were reviewed: Cochrane

Reviews, systematic reviews, general literature reviews,

meta-analyses, randomised controlled trials, prospec-

tive clinical trials, cross-sectional studies and retrospec-

tive cohort studies. Over 400 abstracts were reviewed,

from which more than 50 manuscripts which were

related to stomatognathic function and ⁄ or clinical

K . K O Y A N O et al.514

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evaluation were included. An additional hand search

was also conducted. In addition, technical reports, case

reports, and textbooks that offered anything to the

discussion of the ‘art’ of occlusal rehabilitation were

also included if no strong peer-reviewed evidence such

as randomised controlled clinical trials (RCTs) could be

found.

Mandibular position

Maximal intercuspal position, centric occlusion and centric

relation. Controversy has existed for many years

regarding maximal intercuspal position (ICP), centric

occlusion and centric relation, as illustrated by the

seven different definitions provided for ‘centric rela-

tion’ in the glossary of prosthodontics terms, eighth

edition (GPT-8) (25). According to GPT-8, ‘centric

occlusion’ is defined as ‘the occlusion of opposing teeth

when the mandible is in centric relation. This may or

may not coincide with the maximal intercuspal posi-

tion. This ‘maximal intercuspal position’ is defined as

‘the complete intercuspation of the opposing teeth

independent of condylar position, sometimes referred

to as the best fit of the teeth regardless of the condylar

position’. These descriptions could imply that there are

no absolute definitions for these mandibular positions.

However, it is inevitable for the dentist to employ one

specific mandibular position as a desired occlusion

when confronted with a patient requiring occlusal

rehabilitation. Although there are many varying rec-

ommendations for desired occlusion, no comparative

study has scientifically examined the clinical outcomes

when these different occlusal schemes are used.

From a technical perspective, the reproducibility of

centric relation has been a matter of concern for

dentists aiming to re-establish occlusion in patients in

whom the natural mandibular position has been

lost (e.g. in those with complete dentures). The repro-

ducibility of three commonly reported methods for

recording centric relation (bimanual mandibular

manipulation with a jig; chin point guidance with a

jig; and Gothic arch tracing) was examined in 14

healthy volunteers (26). It was reported that the

bimanual manipulation method positioned the con-

dyles in the temporomandibular joint more consistently

and reproducibly than the other methods. The Gothic

arch was the least consistent method.

According to the lack of evidence from existing

research, there is no clinical study that supports a

specific mandibular position or a specific method for

obtaining desired occlusion is superior to the other in

terms of clinical outcomes.

Occlusal plane

Inclination. There are several studies on the relation-

ship between inclination of the occlusal plane and the

path of masticatory movement (27, 28). Ogawa et al.

(27) reported significant correlation between the incli-

nation of the occlusal plane and the direction of the

closing path during mastication. Sato et al. (28) also

reported that the path of masticatory movement was

closely associated with the occlusal plane. Regarding

bite force, Okane et al. (29) reported that the biting

force during maximum clenching was maximal when

the occlusal plane was made parallel to the ala-tragus

line in their experimental study. However, it should be

noted that the biting force during maximum clenching

is not a measure of clinically relevant stomatognathic

function. Again, no clinical study has examined the

superiority of a specific scheme of occlusal plane over

another in terms of clinical outcomes.

Occlusal guidance (anterior guidance)

Canine protection, group function and balanced occlusion. It

is generally understood that canine guidance is supe-

rior to group function and balanced occlusion in terms

of avoiding traumatic forces to the posterior teeth,

especially in the lateral direction, thus preventing

tooth loss (30–32). However, no comparative studies

have scientifically examined the clinical course of

Table 1. Reviewed issues regarding morphological goals of occlu-

sal treatment

Mandibular position [110]

Maximal intercuspal position, centric occlusion, centric relation

Occlusal plane [44]

Inclination, curvature

Occlusal guidance (anterior guidance) [49]

Occlusal contact [44]

Cusp-to-fossa and cusp-to-ridge occlusal relationships

Tripodisation of cusps

Anatomical teeth vs. non-anatomical teeth

Face-bow transfer [2]

Use of an adjustable articulator [75]

Occlusal support (post-canine occlusal contacts) [102]

The number of articles found in the literature search using

Medline ⁄ PubMed for each topic is provided in square brackets.

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these occlusal schemes on the long-term stability of

occlusion.

From a technical perspective, canine protection

shows greater reproducibility of lateral occlusal contacts

than group function when condylar guidance is set by

different methods in a semi-adjustable articulator.

However, this apparatus may be incapable of reproduc-

ing lateral tooth contacts in cases of group function

with balancing contacts (33). Regarding the influence

of canine guidance on masticatory movement, Ogawa

et al. (34) reported the results of steepening the occlusal

guidance by approximately 10� with a metal overlay on

the lingual surface of the maxillary working-side

canine. This modification was found to significantly

influence the masticatory closing angle, closing time,

occlusal time, stability of the opening angle and the

cycle time in the lateral-type group (n = 9), whereas no

significant changes were found in the vertical-type

group (n = 11). However, it should be noted that

outcomes of studies with artificially changed occlusions

may differ from those with the same occlusal charac-

teristics that are there by nature, and the above-

described results may not be applied in the clinical

situation. With regard to masticatory efficiency in

complete denture wearers, Farias Neto et al. (35)

reported that no significant statistical difference was

found in masticatory efficiency between bilateral bal-

anced occlusion and canine guidance in their double-

blinded controlled crossover clinical trial.

However, a lack of consistency is evident in the

definitions of canine protection and group function and

in methods used to examine them. Ogawa et al. (36)

investigated the occlusal contact pattern of 86 young

adults (aged 20–29 years) with shim stock in regulated

lateral positions (0Æ5, 1, 2 and 3 mm from the maxi-

mum intercuspation). When occlusal contacts were

examined in the total range of lateral positions (0Æ5–

3 mm), only 9Æ3% were classified as being canine-

protected, whereas 45Æ3% and 41Æ9% were classified

into group function and balanced occlusion, respec-

tively. These results were not in agreement with those

of previous studies that reported more canine protec-

tion and less-balanced occlusion when the occlusal

contacts were recorded in an edge-to-edge position or

in an unregulated position.

Although several studies of occlusal guidance have

been published, we have insufficient evidence to

support conclusively the superiority of one scheme

over another in terms of clinical outcomes. In addition,

the lack of consistency in the definitions and examining

methods for determining occlusal guidance is a con-

founding factor in our understanding of this issue.

Occlusal contact

Cusp-to-fossa and cusp-to-ridge occlusal relationships. Cusp-

fossa and cusp-marginal ridge occlusal relationships

represent occlusal arrangements in maximum intercus-

pation (25). In a cusp-fossa occlusal relationship, the

maxillary and mandibular centric cusps articulate with

the opposing fossae. In a cusp-marginal ridge occlusal

relationship, the mandibular second premolar buccal

cusp and mandibular molar mesiobuccal cusps articulate

with the opposing occlusal embrasures. It is advocated

that a cusp-to-fossa occlusal relationship could be supe-

rior to a cusp-to-ridge relationship in terms of preventing

food impaction and lateral forces on posterior teeth (32,

37). However, no comparative study has scientifically

demonstrated the superiority of a cusp-to-fossa over a

cusp-to-ridge occlusal relationship in terms of clinical

outcomes.

Tripodisation of cusps (tripod contacts). Tripodisation of

cusps usually represents an occlusal scheme character-

ised by a cusp-to-fossa relationship in which there are

three points of contact between the cusp and opposing

fossa but with no contact on the cusp tip itself (25). It is

advocated that this occlusal scheme prevents wear of

the cusp tip and reduces lateral forces in the posterior

teeth (32, 37). It is also believed that the cusp-fossa

arrangement, with tripodisation for each working cusp,

enhances occlusal stability and distributes more effec-

tively the forces of occlusion along the axes of teeth.

Unfortunately, there is again no clinical proof to

demonstrate the efficacy of tripodisation in terms of

improving function and ⁄ or clinical outcomes.

Anatomical teeth versus non-anatomical teeth (e.g. lingualised

and flat teeth). Tooth form is purported to influence

masticatory performance. Several experimental studies

evaluated masticatory performance following changes

to the form of artificial teeth in completely and partially

edentulous individuals. In one pilot study, there was no

difference in masticatory performance between lingua-

lised occlusion (n = 14) and bilaterally balanced occlu-

sion (n = 14) in completely edentulous patients treated

with removable complete dentures (38). Conversely, in

a clinical study in which the masticatory efficiency of

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three occlusal forms [0�, 30� and lingual contact

(lingualised occlusion)] was compared in subjects with

mandibular implant overdentures (n = 8), the 0� occlu-

sal form exhibited reduced chewing efficiency. This

occlusal form was characterised by a significantly

higher number of chewing strokes, compared with

the 30� and lingualised forms, but the different occlusal

forms did not influence the clinical or radiographic

detrimental effect of peri-implant soft or hard tissues

(39). In addition, Heydecke et al. (40) reported that the

ability to chew tough foods appears to benefit from the

use of anatomical teeth, when compared with semi-

anatomical lingualised teeth.

A different measure of masticatory function is mixing

ability. Sueda et al. (41) examined the influence of

working side contacts on masticatory function in a

distal extension removable partial denture in five

subjects with edentulous arches from second premolar

to second molar and with opposing natural teeth. They

reported that the mixing ability when discluding on the

working side was increased significantly by a reduction

in the cusp angle of the artificial teeth, but that 10� and

20� decreases in cusp angle did not have significantly

different effects. In addition, working side contacts did

not affect the ability to comminute food.

Finally, regarding the patient’s subjective satisfaction

with the treatment, one RCT indicated that subjects

given complete dentures providing lingualised or ana-

tomical posterior occlusal forms exhibited significantly

higher levels of self-perceived satisfaction assessed by

visual analogue scale than those with zero-degree

posterior occlusal forms (42). However, there are no

other studies of this type to provide further evidential

support.

There is still a controversy regarding the superiority

of an anatomical tooth form over the non-anatomical

ones due to the lack of strong evidence. No long-term

clinical studies have examined the superiority of one

occlusal scheme over any other in terms of clinical

outcomes (43). Similarly, no clinical studies have com-

pared treatments using fixed prostheses owing to the

difficulty in conducting comparative studies for these

devices. In the clinical situation, oral function could

be influenced by other factors such as the retention

and stability of removable dentures, the location and

extent of the tooth loss, the dental status after prosth-

odontic treatment, the treatment modality (e.g. com-

plete dentures or implant-supported overdentures) and

variability in the adaptive capacity of individuals.

Face-bow transfer

The use of a face-bow transfer technique is recom-

mended in many dental textbooks and clinical articles

(23, 44). However, clinical studies have failed to

confirm the superiority of methods using this face-

bow transfer technique over simple methods that do

not require it. Comprehensive methods for the fabrica-

tion of complete dentures including semi-anatomical

lingualised teeth, and a full registration including face-

bow transfer had no significant effect on perceived

chewing ability or patient ratings of denture satisfaction

when compared with simpler procedures (40, 45).

Fabrication of an occlusal appliance, registration and

transfer with an arbitrary earpiece face-bow did not

yield a clinically relevant improvement with regard to

the number of occlusal contacts or the chair-side

adjustment time (46). In fact, in Scandinavia, face-

bows have scarcely been used for the fabrication of

complete dentures during the last two to three decades

with no notable clinical problems (47). Moreover, the

use of the face-bow transfer technique has been

reported to have questionable accuracy and reliability

when used for planning orthognathic surgery (48, 49).

According to the evidence from existing research, no

clinical study has revealed the superiority of the use of a

face-bow transfer technique over simpler methods

without using it in terms of oral function or clinical

outcomes.

Use of an adjustable articulator

The use of an articulator is essential when fabricating

prostheses extraorally and can reduce the time taken

over intra-oral adjustments. From a technical perspec-

tive, it is generally believed that the accurate repro-

duction of patient occlusal relationships and jaw

movements is enhanced when more complicated ⁄ com-

prehensive articulators are used. For instance, the use

of an adjustable articulator is recommended in patients

requiring extensive restorations, for instance those with

reduced occlusal vertical dimension due to severe tooth

wear (50). In orthodontics, the use of a semi-adjustable

articulator is often advocated, such as when significant

discrepancies (>2 mm) exist between retruded contact

position and ICP, where ICP is unstable owing to

multiple missing teeth, and in cases of maxillary

and bimaxillary orthognathic surgery (51). However,

the justification for using articulators for any of the

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above-described indications (i.e. severe tooth wear and

problems requiring orthodontic and ⁄ or orthognathic

surgery) is purely technical (i.e. concerns measures of

accuracy and reproducibility as described earlier)

rather than clinical. No comparative study has shown

a more comprehensive technique to be clinically

superior to simpler ones. Thus, the use of a fully

adjustable articulator for fabricating fixed prostheses

has not been shown to be superior to a simple hinge

articulator in terms of patient oral function or quality

of life (QoL).

In a semi-adjustable articulator, approximately 73%

of protrusive and 81% of lateral excursive contacts

could be reproduced (52), of which 66% and 80%,

respectively, could be duplicated (53). However,

potential sources of error, such as mounting dental

casts on the articulator and registration of interocclusal

relationship, exist in each procedure (51, 54). The

introduction of errors and inaccuracies when using

complicated articulators may explain why general

dentists avoid using fully adjustable articulators.

Again, no clinical study that supports the use of an

adjustable articulator is superior to a simpler articulator

in terms of oral function or clinical outcomes.

Occlusal support (post-canine occlusal contacts)

It is believed that the loss of occlusal support in post-

canine posterior teeth can result in reduced oral

function, and that these deficits could be improved by

re-establishing occlusal contacts. Yurkstas (55) reported

that decreased masticatory efficiency was observed

objectively in individuals lacking occlusal contacts in

the posterior dental arch. Al-Ali et al. (56) also reported

objective assessment of masticatory efficiency in com-

plete denture wearers under experimental conditions

(i.e. where one or more artificial teeth in the mandib-

ular complete denture were removed) significantly

decreased compared with those in the control condi-

tion, in which the artificial posterior teeth were aligned

occlusally with the first and second premolars and the

first molars. Clinical studies have reported objective

improvements to masticatory function by restoring

post-canine occlusal contacts (18, 19). However, the

improvement of masticatory function is reported to

vary between individuals because it is influenced by the

location and extent of the occlusal contact loss and the

condition of the dentition after prosthodontic treatment

(18).

When assessing masticatory function subjectively,

significant variation is seen in the extent of the

perceived disability (20, 21), and clinical studies report

discrepancies between objective and subjective

improvement in oral function following restoration of

post-canine occlusal contacts (18). Moreover, in a study

assessing oral function in individuals with complete

anterior dentition, no significant difference in chewing

ability was apparent between individuals who wore

removable partial dentures (n = 77) and those without

dentures (n = 261) when assessed by structured inter-

views using a self-report six-item chewing index (57).

Several reports have evaluated the impact of reduced

dentition on general and oral health–related QoL. Baba

et al. (58) examined the relationship between missing

occlusal units and oral health–related QoL (oral-health

impact profile, OHIP) in patients (n = 121) with the

shortened dental arch (SDA). They reported that an

increase in one missing occlusal unit was associated

with an increase of 2Æ1 OHIP units in a linear regression

analysis. Missing occlusal units are therefore related to

oral health–related QoL impairment in subjects with

SDAs. Mack et al. (59) conducted a relatively large

epidemiological study of 1406 subjects aged 60–

79 years. They also reported that reduction of the

dentition without replacement of missing teeth by

removable or fixed dentures reduced the physical index

of QoL to the same extent as cancer or renal diseases. In

addition, they found that patients with £9 remaining

teeth were significantly affected on the physical index

of general health-related QoL. Armellini et al. (60),

using OHIP-49 and the Short-Form Health Survey (SF-

36), found that patients with SDAs with an interrupted

anterior region perceived benefits from the insertion of

a removable partial denture, whereas those exhibiting

SDAs with intact anterior regions did not.

Regarding the long-term stability of the dentition,

Witter et al. (61) conducted a 9-year observation study

and reported that individuals with SDAs (n = 42)

showed reasonable occlusal stability with only minor

changes (such as increased interdental spacing in the

premolar region and more occlusal contacts in anterior

teeth) than did patients with complete dental arches

(n = 41). From the same study samples, Witter et al.

(62) also reported that individuals with SDAs had

similar prevalence, severity, and fluctuation of

signs and symptoms related to TMD as those with

complete dental arches in their 9-year follow-up

study. In addition, Sarita et al. (63) reported, in their

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cross-sectional epidemiological study, that no strong

evidence was found that a SDA provokes signs and

symptoms associated with TMD, even though the risk

for pain and joint sounds might increase when all

posterior support was unilaterally or bilaterally absent.

According to the evidence from existing research, the

following conclusion can be drawn regarding occlusal

supports in terms of occlusal rehabilitation. Objective

oral function could be improved by increasing the

number of occlusal contacts through prosthetic treat-

ments. However, the magnitude of improvement is

likely to be influenced by the location and extent of the

loss of occlusal supports, the dental status after prosth-

odontic treatment, the treatment modality (e.g.

implants or removable partial dentures) and variability

in the adaptive capacity of individuals. Moreover, the

improvement of subjective oral function may not be

correlated with that of objective function. The concept

of a ‘SDA’ (64) should be considered as a practical

occlusal scheme in the clinical situation.

Discussion

Although there are many studies in which specific

occlusal schemes have been examined, most demon-

strate poor study design and ambiguous results and are

thus of low quality. There are also many studies in

which changes in stomatognathic function with artifi-

cially changed occlusions were examined. However, it

should be noted that artificially changed occlusions for

sake of experiments cannot be compared with naturally

existing occlusions and the obtained results may not be

applied in the clinical situation. Few RCTs have exam-

ined the clinical outcomes of prosthetic treatments

using removable prostheses for different occlusal

schemes, for re-establishing occlusal contacts of post-

canine teeth and for examining the utility of the SDA

scheme in the clinical situation.

Regarding the patients’ and clinical factors, it was

demonstrated that quality of complete dentures, such

as retention and stability of mandibular dentures and

accuracy of reproduction of retruded jaw relationship,

and patients’ adaptability factors were powerful deter-

minants of patients’ satisfaction with new complete

dentures (65). This may indicate that a careful clinical

examination and accurate clinical procedures can

improve the treatment outcome of prosthetic treatments.

On the other hand, it is also understood that other

factors such as neurophysiological and psychosocial

factors can influence the clinical outcomes of treat-

ments. Several studies clearly demonstrated that per-

sonality factors had significant associations with denture

satisfaction (66, 67), and that dentists’ and patients’

interpersonal appraisals of each other were the most

significant factors accounting for patient outcome dif-

ferences (68). Establishing a good patient–dentist rela-

tionship may be one of the keys to the clinical success.

Overall, there is no strong evidence to support the

superiority of a specific occlusal scheme over another in

terms of improving stomatognathic function or clinical

outcomes. Similarly, strong evidence is lacking to

justify the use of sophisticated systems (such as face-

bow transfer and adjustable articulators) to improve

stomatognathic function and clinical results compared

with those using simpler methods. Studies with the best

possible research designs must be conducted to solve

the above-described controversies.

Conclusion

There is no strong evidence to conclude that a specific

occlusal scheme is superior to any other in terms of

improving stomatognathic function or clinical out-

comes. Evidence is lacking to justify the use of sophis-

ticated systems to enhance stomatognathic function

and improve clinical results compared with those using

simpler methods.

Nevertheless, this must be interpreted carefully, and

the distinction between ‘no evidence of effects’ of the

treatments and ‘evidence of no effects’ must be

emphasised. Although occlusal rehabilitation can be

conducted successfully by simple methods, it should

always be managed by accurate, reproducible, rapid

and easy procedures that are applied with strong

clinical skills to reduce unnecessary technical failures

and ⁄ or the requirement for compensatory adjustments.

Despite the lack of strong scientific evidence, these skills

are still essential for dentists aiming to treat patients

who require occlusal rehabilitation. Furthermore,

attaining profound knowledge and skills in postgradu-

ate training will be necessary for prosthodontic special-

ists who should be in charge of complicated cases.

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Correspondence: Kiyoshi Koyano, Section of Implant and Rehabilita-

tive Dentistry, Division of Oral Rehabilitation, Faculty of Dental

Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka

812-8582, Japan. E-mail: koyano@dent.kyushu-u.ac.jp

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