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Transcript of j.1365-2842.2012.02303.x
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
ª 2012 Blackwell Publishing Ltd
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.
R E H A B I L I T A T I O N O F O C C L U S I O N 515
ª 2012 Blackwell Publishing Ltd
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
K . K O Y A N O et al.516
ª 2012 Blackwell Publishing Ltd
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
R E H A B I L I T A T I O N O F O C C L U S I O N 517
ª 2012 Blackwell Publishing Ltd
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
K . K O Y A N O et al.518
ª 2012 Blackwell Publishing Ltd
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: [email protected]
R E H A B I L I T A T I O N O F O C C L U S I O N 521
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