Rehabilitation of occlusion – science or art

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Rehabilitation of occlusion – science or art

  1. 1. Journal of Oral RehabilitationJournal of Oral Rehabilitation 2012 39; 513–521Review ArticleRehabilitation of occlusion – science or art?K. KOYANO, Y. TSUKIYAMA & R. KUWATSURU Section of Implant and Rehabilitative Dentistry, Division ofOral Rehabilitation, Faculty of Dental Science, Kyushu University, Fukuoka, JapanSUMMARY The primary objective of rehabilitating were poorly designed and of low quality, thusocclusion is to improve stomatognathic function in yielding ambiguous results. Overall, there is nopatients experiencing dysfunction in mastication, scientific evidence that supports any specificspeech, and swallowing as a consequence of tooth occlusal scheme being superior to others in termsloss. The procedure of occlusal treatment involves of improving stomatognathic function, nor thatimproving the morphology and the stomatognathic sophisticated methods are superior to simpler onesfunction. Several practical methods and morpholog- in terms of clinical outcomes. However, it is obviousical endpoints have been described in occlusal reha- that the art of occlusal rehabilitation requires accu-bilitation. We made a selection of these (mandibular rate, reproducible, easy and quick procedures toposition, occlusal plane, occlusal guidance, occlusal reduce unnecessary technical failures and ⁄ or thecontact, face-bow transfer, use of an adjustable requirement for compensatory adjustments. There-articulator and occlusal support) and performed a fore, despite the lack of scientific evidence forliterature review to verify the existence of compel- specific treatments, the acquisition of these generalling scientific evidence for each of these. A literature skills by dentists and attaining profound knowledgesearch was conducted using Medline ⁄ PubMed in and skills in postgraduate training will be necessaryMarch 2011. Over 400 abstracts were reviewed, and for specialists in charge of complicated cases.more than 50 manuscripts selected. An additional KEYWORDS: occlusion, rehabilitation, clinical evi-hand search was also conducted. Of the many dence, technique, skillstudies investigating stomatognathic function inrelation to specific occlusal schemes, most studies Accepted for publication 17 February 2012 treatments to improve morphology (e.g. fabricatingIntroduction prostheses based on morphological requirements) andDentists aim to rehabilitate occlusion in patients for a consequently intend to improve stomatognathic func-variety of reasons including extreme reduction in the tion. A method of occlusal rehabilitation that certainlyvertical dimension of occlusion owing to severe dental improves function is not yet available. These ‘indirect’wear and severe aesthetic ⁄ phonetic disturbance result- methods, that is, improving function by providing aning from maxillary resection to aid tumour removal. appropriate morphology, are nevertheless superior toAesthetics is especially important when the maxillary other prostheses, such as eye prostheses, that areanterior region is to be rehabilitated. In most cases, morphologically correct and have adequate aestheticshowever, the primary objective of occlusal rehabilita- but cannot improve function (e.g. vision).tion is to improve the stomatognathic function of The assumption that improved stomatognathic func-patients who have dysfunction or disability in mastica- tion can be achieved by providing good morphology istion, speech or swallowing because of either tooth loss logical only if there is a close positive relationshipor other reasons. We can currently only provide between morphology and function such that good morphology can produce and maintain better function.Based on a presentation at CORE China 2011. Hence, several questions need to be answered. First,ª 2012 Blackwell Publishing Ltd doi: 10.1111/j.1365-2842.2012.02303.x
  2. 2. 514 K . K O Y A N O et al. can we improve function and ⁄ or reduce disability by Finally, regarding occlusal rehabilitation as a means providing good morphology? Second, can we prevent of re-establishing occlusal contacts, studies have deterioration of function by correcting morphology? reported functional improvement following restoration Finally, can we prove causality in the above-described of occlusal contacts between post-canine teeth (18, 19). issues? The objective masticatory function (chewing perfor- As an example, the relationship between temporo- mance) was significantly improved by the insertion of mandibular disorders (TMD) and occlusion has been removable partial dentures or fixed prostheses in 15 discussed for many years. One major concept among patients who had missing post-canine teeth (18). It is the early aetiologic theories for TMD was the suggestion also reported that masticatory performance signifi- that abnormal occlusal contacts were causal factors (1– cantly increased after the insertion of an implant 4). Extensive studies including systematic reviews have prosthesis in the second molar region (19). However, revealed that there is no strong relationship between considerable variation was found in the perceived occlusal problems and TMD as previously believed. disability in individuals with missing teeth (20, 21), There is no strong evidence to support the superiority of and discrepancy between objective and subjective occlusal treatment over any other treatment modalities measures of oral functional improvement was reported (e.g. cognitive behavioural, pharmacological or physical (18). The following section addresses these issues in therapies) nor that providing a ‘good’ occlusion can more detail. prevent the occurrence of TMD (5, 6). Another example is the link between bruxism and Morphological goals of occlusal treatment occlusion. The three main classes of factors causing sleep bruxism are neurological, peripheral (e.g. occlu- Several theoretical ⁄ morphological goals for occlusal sion) and psychogenic, of which occlusal problems treatment can be drawn from dental literature. These were considered the major aetiological factor (7). include mandibular position, occlusal plane, occlusal Although the aetiology and neurological mechanisms guidance, occlusal contact, face-bow transfer, use of an that generate sleep bruxism are not exactly understood, adjustable articulator and occlusal support (22, 23). a number of studies have proven that central factors Most of these are based on the theoretical concept of an play a major role in its development (8–12), which ‘ideal’ occlusion, which is rarely found in the natural appears to be induced within the central nervous dentition (24). system (9, 13). Moreover, several studies showed that We performed a literature review to examine the altered inputs from peripheral oral receptors resulting existence and strength of scientific evidence for each of from realignment of occlusal contacts or increased these morphological goals of occlusion (Table 1). A occlusal vertical dimension temporarily diminishes, search of the English-language literature was con- but does not stop, bruxism (14, 15). In a randomised ducted using Medline ⁄ PubMed in March 2011. Search controlled crossover clinical trial, in which the effect of terms and MEDLINE Medical Subject Headings for the stabilisation splints and palatal splints (which have zero search included ‘occlusion (dental occlusion)’ and coverage of the occlusal surfaces) on sleep bruxism was ‘rehabilitation’, with various combinations of these examined, both splint designs significantly reduced terms with ‘mandibular position’, ‘intercuspal position’, sleep bruxism, but the effect was only transient (16). ‘centric occlusion’, ‘centric relation’, ‘occlusal plane’, Also, a double-blind, parallel, controlled, randomised ‘inclination’, ‘curvature’, ‘guidance (occlusal guidance clinical trial revealed that stabilisation splints were not and anterior guidance)’, ‘occlusal contact’, ‘artificial efficient in reducing sleep bruxism in a 4-week obser- tooth ⁄ teeth’, ‘face-bow or facebow’, ‘articulator (dental vation period (17). It is suggested that changing occlusal articulators)’ and ‘occlusal support’. Abstracts of the contacts with occlusal splints may not be a primary following types of articles were reviewed: Cochrane factor in reducing sleep bruxism activity. To date, the Reviews, systematic reviews, general literature reviews, accumulated evidence looks neither convincing nor meta-analyses, randomised controlled trials, prospec- powerful enough to state conclusively that occlusal tive clinical trials, cross-sectional studies and retrospec- treatment prevents sleep bruxism, and occlusal therapy tive cohort studies. Over 400 abstracts were reviewed, is therefore not recommended as a primary method for from which more than 50 manuscripts which were managing this condition. related to stomatognathic function and ⁄ or clinical ª 2012 Blackwell Publishing Ltd
  3. 3. REHABILITATION OF OCCLUSION 515Table 1. Reviewed issues regarding morphological goals of occlu- From a technical perspective, the reproducibility ofsal treatment centric relation has been a matter of concern for dentists aiming to re-establish occlusion in patients inMandibular position [110] whom the natural mandibular position has been Maximal intercuspal position, centric occlusion, centric relationOcclusal plane [44] lost (e.g. in those with complete dentures). The repro- Inclination, curvature ducibility of three commonly reported methods forOcclusal guidance (anterior guidance) [49] recording centric relation (bimanual mandibularOcclusal contact [44] manipulation with a jig; chin point guidance with a Cusp-to-fossa and cusp-to-ridge occlusal relationships jig; and Gothic arch tracing) was examined in 14 Tripodisation of cusps Anatomical teeth vs. non-anatomical teeth healthy volunteers (26). It was reported that theFace-bow transfer [2] bimanual manipulation method positioned the con-Use of an adjustable articulator [75] dyles in the temporomandibular joint more consistentlyOcclusal support (post-canine occlusal contacts) [102] and reproducibly than the other methods. The GothicThe number of articles found in the literature search using arch was the least consistent method.Medline ⁄ PubMed for each topic is provided in square brackets. According to the lack of evidence from existing research, there is no clinical study that supports aevaluation were included. An additional hand search specific mandibular position or a specific method forwas also conducted. In addition, technical reports, case obtaining desired occlusion is superior to the other inreports, and textbooks that offered anything to the terms of clinical outcomes.discussion of the ‘art’ of occlusal rehabilitation werealso included if no strong peer-reviewed evidence such Occlusal planeas randomised controlled clinical trials (RCTs) could befound. 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.Mandibular position (27) reported significant correlation between the incli-Maximal intercuspal position, centric occlusion and centric nation of the occlusal plane and the direction of therelation. Controversy has existed for many years closing path during mastication. Sato et al. (28) alsoregarding maximal intercuspal position (ICP), centric reported that the path of masticatory movement wasocclusion and centric relation, as illustrated by the closely associated with the occlusal plane. Regardingseven different definitions provided for ‘centric rela- bite force, Okane et al. (29) reported that the bitingtion’ in the glossary of prosthodontics terms, eighth force during maximum clenching was maximal whenedition (GPT-8) (25). According to GPT-8, ‘centric the occlusal plane was made parallel to the ala-tragusocclusion’ is defined as ‘the occlusion of opposing teeth line in their experimental study. However, it should bewhen the mandible is in centric relation. This may or noted that the biting force during maximum clenchingmay not coincide with the maximal intercuspal posi- is not a measure of clinically relevant stomatognathiction. This ‘maximal intercuspal position’ is defined as function. Again, no clinical study has examined the‘the complete intercuspation of the opposing teeth superiority of a specific scheme of occlusal plane overindependent of condylar position, sometimes referred another in terms of clinical outcomes.to as the best fit of the teeth regardless of the condylarposition’. These descriptions could imply that there are Occlusal guidance (anterior guidance)no absolute definitions for these mandibular positions.However, it is inevitable for the dentist to employ one Canine protection, group function and balanced occlusion. Itspecific mandibular position as a desired occlusion is generally understood that canine guidance is supe-when confronted with a patient requiring occlusal rior to group function and balanced occlusion in termsrehabilitation. Although there are many varying rec- of avoiding traumatic forces to the posterior teeth,ommendations for desired occlusion, no comparative especially in the lateral direction, thus preventingstudy has scientifically examined the clinical outcomes tooth loss (30–32). However, no comparative studieswhen these different occlusal schemes are used. have scientifically examined the clinical course ofª 2012 Blackwell Publishing Ltd
  4. 4. 516 K . K O Y A N O et al. these occlusal schemes on the long-term stability of the lack of consistency in the definitions and examining occlusion. methods for determining occlusal guidance is a con- From a technical perspective, canine protection founding factor in our understanding of this issue. shows greater reproducibility of lateral occlusal contacts than group function when condylar guidance is set by Occlusal contact different methods in a semi-adjustable articulator. However, this apparatus may be incapable of reproduc- Cusp-to-fossa and cusp-to-ridge occlusal relationships. Cusp- ing lateral tooth contacts in cases of group function fossa and cusp-marginal ridge occlusal relationships with balancing contacts (33). Regarding the influence represent occlusal arrangements in maximum intercus- of canine guidance on masticatory movement, Ogawa pation (25). In a cusp-fossa occlusal relationship, the et al. (34) reported the results of steepening the occlusal maxillary and mandibular centric cusps articulate with guidance by approximately 10° with a metal overlay on the opposing fossae. In a cusp-marginal ridge occlusal the lingual surface of the maxillary working-side relationship, the mandibular second premolar buccal canine. This modification was found to significantly cusp and mandibular molar mesiobuccal cusps articulate influence the masticatory closing angle, closing time, with the opposing occlusal embrasures. It is advocated occlusal time, stability of the opening angle and the that a cusp-to-fossa occlusal relationship could be supe- cycle time in the lateral-type group (n = 9), whereas no rior to a cusp-to-ridge relationship in terms of preventing significant changes were found in the vertical-type food impaction and lateral forces on posterior teeth (32, group (n = 11). However, it should be noted that 37). However, no comparative study has scientifically outcomes of studies with artificially changed occlusions demonstrated the superiority of a cusp-to-fossa over a may differ from those with the same occlusal charac- cusp-to-ridge occlusal relationship in terms of clinical teristics that are there by nature, and the above- outcomes. described results may not be applied in the clinical situation. With regard to masticatory efficiency in Tripodisation of cusps (tripod contacts). Tripodisation of complete denture wearers, Farias Neto et al. (35) cusps usually represents an occlusal scheme character- reported that no significant statistical difference was ised by a cusp-to-fossa relationship in which there are found in masticatory efficiency between bilateral bal- three points of contact between the cusp and opposing anced occlusion and canine guidance in their double- fossa but with no contact on the cusp tip itself (25). It is blinded controlled crossover clinical trial. advocated that this occlusal scheme prevents wear of However, a lack of consistency is evident in the the cusp tip and reduces lateral forces in the posterior definitions of canine protection and group function and teeth (32, 37). It is also believed that the cusp-fossa in methods used to examine them. Ogawa et al. (36) arrangement, with tripodisation for each working cusp, investigated the occlusal contact pattern of 86 young enhances occlusal stability and distributes more effec- adults (aged 20–29 years) with shim stock in regulated tively the forces of occlusion along the axes of teeth. lateral positions (0Æ5, 1, 2 and 3 mm from the maxi- Unfortunately, there is again no clinical proof to mum intercuspation). When occlusal contacts were demonstrate the efficacy of tripodisation in terms of examined in the total range of lateral positions (0Æ5– improving function and ⁄ or clinical outcomes. 3 mm), only 9Æ3% were classified as being canine- protected, whereas 45Æ3% and 41Æ9% were classified Anatomical teeth versus non-anatomical teeth (e.g. lingualised into group function and balanced occlusion, respec- and flat teeth). Tooth form is purported to influence tively. These results were not in agreement with those masticatory performance. Several experimental studies of previous studies that reported more canine protec- evaluated masticatory performance following changes tion and less-balanced occlusion when the occlusal to the form of artificial teeth in completely and partially contacts were recorded in an edge-to-edge position or edentulous individuals. In one pilot study, there was no in an unregulated position. difference in masticatory performance between lingua- Although several studies of occlusal guidance have lised occlusion (n = 14) and bilaterally balanced occlu- been published, we have insufficient evidence to sion (n = 14) in completely edentulous patients treated support conclusively the superiority of one scheme with removable complete dentures (38). Conversely, in over another in terms of clinical outcomes. In addition, a clinical study in which the masticatory efficiency of ª 2012 Blackwell Publishing Ltd
  5. 5. REHABILITATION OF OCCLUSION 517three occlusal forms [0°, 30° and lingual contact Face-bow transfer(lingualised occlusion)] was compared in subjects withmandibular implant overdentures (n = 8), the 0° occlu- The use of a face-bow transfer technique is recom-sal form exhibited reduced chewing efficiency. This mended in many dental textbooks and clinical articlesocclusal form was characterised by a significantly (23, 44). However, clinical studies have failed tohigher number of chewing strokes, compared with confirm the superiority of methods using this face-the 30° and lingualised forms, but the different occlusal bow transfer technique over simple methods that doforms did not influence the clinical or radiographic not require it. Comprehensive methods for the fabrica-detrimental effect of peri-implant soft or hard tissues tion of complete dentures including semi-anatomical(39). In addition, Heydecke et al. (40) reported that the lingualised teeth, and a full registration including face-ability to chew tough foods appears to benefit from the bow transfer had no significant effect on perceiveduse of anatomical teeth, when compared with semi- chewing ability or patient ratings of denture satisfactionanatomical lingualised teeth. when compared with simpler procedures (40, 45). A different measure of masticatory function is mixing Fabrication of an occlusal appliance, registration andability. Sueda et al. (41) examined the influence of transfer with an arbitrary earpiece face-bow did notworking side contacts on masticatory function in a yield a clinically relevant improvement with regard todistal extension removable partial denture in five the number of occlusal contacts or the chair-sidesubjects with edentulous arches from second premolar adjustment time (46). In fact, in Scandinavia, face-to second molar and with opposing natural teeth. They bows have scarcely been used for the fabrication ofreported that the mixing ability when discluding on the complete dentures during the last two to three decadesworking side was increased significantly by a reduction with no notable clinical problems (47). Moreover, thein the cusp angle of the artificial teeth, but that 10° and use of the face-bow transfer technique has been20° decreases in cusp angle did not have significantly reported to have questionable accuracy and reliabilitydifferent effects. In addition, working side contacts did when used for planning orthognathic surgery (48, 49).not affect the ability to comminute food. According to the evidence from existing research, no Finally, regarding the patient’s subjective satisfaction clinical study has revealed the superiority of the use of awith the treatment, one RCT indicated that subjects face-bow transfer technique over simpler methodsgiven complete dentures providing lingualised or ana- without using it in terms of oral function or clinicaltomical posterior occlusal forms exhibited significantly outcomes.higher levels of self-perceived satisfaction assessed byvisual analogue scale than those with zero-degree Use of an adjustable articulatorposterior occlusal forms (42). However, there are noother studies of this type to provide further evidential The use of an articulator is essential when fabricatingsupport. prostheses extraorally and can reduce the time taken There is still a controversy regarding the superiority over intra-oral adjustments. From a technical perspec-of an anatomical tooth form over the non-anatomical tive, it is generally believed that the accurate repro-ones due to the lack of strong evidence. No long-term duction of patient occlusal relationships and jawclinical studies have examined the superiority of one movements is enhanced when more complicated ⁄ com-occlusal scheme over any other in terms of clinical prehensive articulators are used. For instance, the useoutcomes (43). Similarly, no clinical studies have com- of an adjustable articulator is recommended in patientspared treatments using fixed prostheses owing to the requiring extensive restorations, for instance those withdifficulty in conducting comparative studies for these reduced occlusal vertical dimension due to severe toothdevices. In the clinical situation, oral function could wear (50). In orthodontics, the use of a semi-adjustablebe influenced by other factors such as the retention articulator is often advocated, such as when significantand stability of removable dentures, the location and discrepancies (>2 mm) exist between retruded contactextent of the tooth loss, the dental status after prosth- position and ICP, where ICP is unstable owing toodontic treatment, the treatment modality (e.g. com- multiple missing teeth, and in cases of maxillaryplete dentures or implant-supported overdentures) and and bimaxillary orthognathic surgery (51). However,variability in the adaptive capacity of individuals. the justification for using articulators for any of theª 2012 Blackwell Publishing Ltd
  6. 6. 518 K . K O Y A N O et al. above-described indications (i.e. severe tooth wear and When assessing masticatory function subjectively, problems requiring orthodontic and ⁄ or orthognathic significant variation is seen in the extent of the surgery) is purely technical (i.e. concerns measures of perceived disability (20, 21), and clinical studies report accuracy and reproducibility as described earlier) discrepancies between objective and subjective rather than clinical. No comparative study has shown improvement in oral function following restoration of a more comprehensive technique to be clinically post-canine occlusal contacts (18). Moreover, in a study superior to simpler ones. Thus, the use of a fully assessing oral function in individuals with complete adjustable articulator for fabricating fixed prostheses anterior dentition, no significant difference in chewing has not been shown to be superior to a simple hinge ability was apparent between individuals who wore articulator in terms of patient oral function or quality removable partial dentures (n = 77) and those without of life (QoL). dentures (n = 261) when assessed by structured inter- In a semi-adjustable articulator, approximately 73% views using a self-report six-item chewing index (57). of protrusive and 81% of lateral excursive contacts Several reports have evaluated the impact of reduced could be reproduced (52), of which 66% and 80%, dentition on general and oral health–related QoL. Baba respectively, could be duplicated (53). However, et al. (58) examined the relationship between missing potential sources of error, such as mounting dental occlusal units and oral health–related QoL (oral-health casts on the articulator and registration of interocclusal impact profile, OHIP) in patients (n = 121) with the relationship, exist in each procedure (51, 54). The shortened dental arch (SDA). They reported that an introduction of errors and inaccuracies when using increase in one missing occlusal unit was associated complicated articulators may explain why general with an increase of 2Æ1 OHIP units in a linear regression dentists avoid using fully adjustable articulators. analysis. Missing occlusal units are therefore related to Again, no clinical study that supports the use of an oral health–related QoL impairment in subjects with adjustable articulator is superior to a simpler articulator SDAs. Mack et al. (59) conducted a relatively large in terms of oral function or clinical outcomes. epidemiological study of 1406 subjects aged 60– 79 years. They also reported that reduction of the dentition without replacement of missing teeth by Occlusal support (post-canine occlusal contacts) removable or fixed dentures reduced the physical index It is believed that the loss of occlusal support in post- of QoL to the same extent as cancer or renal diseases. In canine posterior teeth can result in reduced oral addition, they found that patients with £9 remaining function, and that these deficits could be improved by teeth were significantly affected on the physical index re-establishing occlusal contacts. Yurkstas (55) reported of general health-related QoL. Armellini et al. (60), that decreased masticatory efficiency was observed using OHIP-49 and the Short-Form Health Survey (SF- objectively in individuals lacking occlusal contacts in 36), found that patients with SDAs with an interrupted the posterior dental arch. Al-Ali et al. (56) also reported anterior region perceived benefits from the insertion of objective assessment of masticatory efficiency in com- a removable partial denture, whereas those exhibiting plete denture wearers under experimental conditions SDAs with intact anterior regions did not. (i.e. where one or more artificial teeth in the mandib- Regarding the long-term stability of the dentition, ular complete denture were removed) significantly Witter et al. (61) conducted a 9-year observation study decreased compared with those in the control condi- and reported that individuals with SDAs (n = 42) tion, in which the artificial posterior teeth were aligned showed reasonable occlusal stability with only minor occlusally with the first and second premolars and the changes (such as increased interdental spacing in the first molars. Clinical studies have reported objective premolar region and more occlusal contacts in anterior improvements to masticatory function by restoring teeth) than did patients with complete dental arches post-canine occlusal contacts (18, 19). However, the (n = 41). From the same study samples, Witter et al. improvement of masticatory function is reported to (62) also reported that individuals with SDAs had vary between individuals because it is influenced by the similar prevalence, severity, and fluctuation of location and extent of the occlusal contact loss and the signs and symptoms related to TMD as those with condition of the dentition after prosthodontic treatment complete dental arches in their 9-year follow-up (18). study. In addition, Sarita et al. (63) reported, in their ª 2012 Blackwell Publishing Ltd
  7. 7. REHABILITATION OF OCCLUSION 519cross-sectional epidemiological study, that no strong factors can influence the clinical outcomes of treat-evidence was found that a SDA provokes signs and ments. Several studies clearly demonstrated that per-symptoms associated with TMD, even though the risk sonality factors had significant associations with denturefor pain and joint sounds might increase when all satisfaction (66, 67), and that dentists’ and patients’posterior support was unilaterally or bilaterally absent. interpersonal appraisals of each other were the most According to the evidence from existing research, the significant factors accounting for patient outcome dif-following conclusion can be drawn regarding occlusal ferences (68). Establishing a good patient–dentist rela-supports in terms of occlusal rehabilitation. Objective tionship may be one of the keys to the clinical success.oral function could be improved by increasing the Overall, there is no strong evidence to support thenumber of occlusal contacts through prosthetic treat- superiority of a specific occlusal scheme over another inments. However, the magnitude of improvement is terms of improving stomatognathic function or clinicallikely to be influenced by the location and extent of the outcomes. Similarly, strong evidence is lacking toloss of occlusal supports, the dental status after prosth- justify the use of sophisticated systems (such as face-odontic treatment, the treatment modality (e.g. bow transfer and adjustable articulators) to improveimplants or removable partial dentures) and variability stomatognathic function and clinical results comparedin the adaptive capacity of individuals. Moreover, the with those using simpler methods. Studies with the bestimprovement of subjective oral function may not be possible research designs must be conducted to solvecorrelated with that of objective function. The concept the above-described controversies.of a ‘SDA’ (64) should be considered as a practicalocclusal scheme in the clinical situation. Conclusion There is no strong evidence to conclude that a specificDiscussion occlusal scheme is superior to any other in terms ofAlthough there are many studies in which specific improving stomatognathic function or clinical out-occlusal schemes have been examined, most demon- comes. Evidence is lacking to justify the use of sophis-strate poor study design and ambiguous results and are ticated systems to enhance stomatognathic functionthus of low quality. There are also many studies in and improve clinical results compared with those usingwhich changes in stomatognathic function with artifi- simpler methods.cially changed occlusions were examined. However, it Nevertheless, this must be interpreted carefully, andshould be noted that artificially changed occlusions for the distinction between ‘no evidence of effects’ of thesake of experiments cannot be compared with naturally treatments and ‘evidence of no effects’ must beexisting occlusions and the obtained results may not be emphasised. Although occlusal rehabilitation can beapplied in the clinical situation. Few RCTs have exam- conducted successfully by simple methods, it shouldined the clinical outcomes of prosthetic treatments always be managed by accurate, reproducible, rapidusing removable prostheses for different occlusal and easy procedures that are applied with strongschemes, for re-establishing occlusal contacts of post- clinical skills to reduce unnecessary technical failurescanine teeth and for examining the utility of the SDA and ⁄ or the requirement for compensatory adjustments.scheme in the clinical situation. Despite the lack of strong scientific evidence, these skills Regarding the patients’ and clinical factors, it was are still essential for dentists aiming to treat patientsdemonstrated that quality of complete dentures, such who require occlusal rehabilitation. Furthermore,as retention and stability of mandibular dentures and attaining profound knowledge and skills in postgradu-accuracy of reproduction of retruded jaw relationship, ate training will be necessary for prosthodontic special-and patients’ adaptability factors were powerful deter- ists who should be in charge of complicated cases.minants of patients’ satisfaction with new completedentures (65). This may indicate that a careful clinicalexamination and accurate clinical procedures can Referencesimprove the treatment outcome of prosthetic treatments. 1. Angle EG. Treatment of malocclusion of the teeth andOn the other hand, it is also understood that other fractures of the maxillae: Angle’s system. 6th ed. Philadelphiafactors such as neurophysiological and psychosocial (PA): SS White Dental Manufacturing Co, 1900.ª 2012 Blackwell Publishing Ltd
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