Kazuyoshi Baba

Sixty-eight years of experimental occlusal interference studies: what have we learned?

STATEMENT OF PROBLEMnUnderstanding is needed regarding the effect that occlusal interferences have on the teeth, periodontium, and especially on jaw function.nnnPURPOSEnThis article summarizes research in which experimental occlusal interferences have been placed on the teeth of animals and human volunteers.nnnMATERIAL AND METHODSnData from 18 human and 10 animals studies were reviewed. Experimental occlusal interferences were grouped into those that alter intercuspal position and those contacting on lateral jaw movement only. The outcome of these interferences were analyzed according to their local pulpal-periodontal, jaw function, or bruxism effects.nnnRESULTSnExperimental occlusal interferences in maximum intercuspation had a deleterious effect on periodontal and pulpal tissues of the affected tooth; sometimes this produces a disruption of smooth jaw function and occasionally jaw muscle pain and clicking. Experimental occlusal interferences that contact only in a lateral jaw movement are infrequently harmful to jaw function. Furthermore, no reliable evidence demonstrates that occlusal interferences can cause nocturnal bruxism, or stop it.nnnCONCLUSIONnTransient local tooth pain, loosening of the tooth, a slight change in postural muscle tension levels, chewing stroke patterns, and sometimes a clicking joint can be induced by an experimental occlusal interference. Because such findings are present in relatively asymptomatic patients, these data do not prove that occlusal interferences are causally related to a chronic jaw muscle pain or temporomandibular joint dysfunction problems.

Reliability, validity, and utility of various occlusal measurement methods and techniques

STATEMENT OF PROBLEMnThe controversy continues regarding the efficacy of several commercially available devices that are used as aids in the diagnosis of occlusal abnormalities.nnnPURPOSEnThis article reviews the reliability, validity, and utility of instruments that claim to detect occlusal interferences and abnormal vertical dimension of occlusion.nnnMATERIAL AND METHODSnData, opinions, and technical information from 37 published articles were reviewed. Evidence for method reliability, validity, and utility was assessed.nnnRESULTSnAlthough occlusal contact detection devices can document the occlusal contact patterns on teeth, the basic in vivo testing of their reproducibility and validity has not been performed. Moreover, while EMG and jaw tracking systems can indeed measure jaw muscle activation and jaw position, no cost-benefit analysis of these devices has yet been conducted. One manufacturer suggests that these instruments be used in conjunction with an electrical muscle stimulation device to find a new resting jaw position that is more open vertically. This new, more open position has been inappropriately labeled as evidence of vertical dimension of occlusion over-closure.nnnCONCLUSIONnNone of the instruments reviewed can be said to be more than ancillary documentation devices and they have been inadequately tested for reliability and validity. Moreover, because scientifically acceptable disease definitions are not available for these 2 conditions, the issue of over-diagnosing becomes a substantial concern.

The validity and utility of disease detection methods and of occlusal therapy for temporomandibular disorders.

Our evaluation of the clinical usefulness or devices for the diagnosis or treatment of temporomandibular disorders (TMD) led to the conclusion that the only current gold standard for TMD is a global clinical examination, because none of the instruments can be said to provide more than ancillary documentation and none have proven diagnostic validity or utility. Regarding the therapeutic efficacy of occlusal adjustment, we could find no comparative studies that test the efficacy of occlusal adjustment in preventing TMD. The studies we reviewed on the relationship of occlusion to TMD are not convincing, powerful, or practical enough to make any recommendations about a causal association.

Feasibility of oral health‐related quality of life assessment in prosthodontic patients using abbreviated Oral Health Impact Profile questionnaires

To report about the feasibility of oral health-related quality of life assessment using two short forms of the Oral Health Impact Profile - OHIP-J14 and OHIP-J5 - in prosthodontic patients. Using the item pool of the Japanese version of the OHIP, two short forms based on a 14-item English-language version and a 5-item German-language questionnaire were derived. To test construct validity, the associations between summary scores of two short versions and self-reported oral health and self-reported denture quality have been investigated. Responsiveness was tested in 30 patients treated for their removable partial denture. Test-retest reliability using a time interval of 2 weeks and internal consistency were also tested. Associations between the two short form summary scores and self-reported oral health and denture quality supported construct validity of the instruments. Acceptable reliability for OHIP-J14 and OHIP-J5 was indicated by intra-class correlation coefficients of 0.73 and 0.75 (test-retest reliability) and CRONBACHS alpha of 0.94 and 0.81 (internal consistency) respectively. Responsiveness was sufficient for OHIP-J14 and OHIP-J5 indicated by medium effect sizes (0.50 and 0.57 respectively). In addition to sufficient discriminative psychometric properties, the ability to measure change of perceived oral health make OHIP-J14 and OHIP-J5 suitable for outcomes research.

Influence of protrusive tooth contact on tapping point distribution.

This study investigated the influence of protrusive tooth contacts (tooth contacts during mandibular protrusion) on the tapping point distribution. Nine healthy subjects volunteered for this study and the protrusive tooth contact pattern, as well as the retrusive tooth contact pattern, was altered on four maxillary occlusal splints. The first splint was adjusted to make the sagittal incisal path of protrusion and retrusion equivalent to that of the natural dentition. The second and third splints had partial and complete elimination of the protrusive tooth contact, respectively. The fourth splint had complete elimination of both protrusive and retrusive tooth contacts. The subjects were asked to use each splint continuously for 1 week. The tapping point distribution was measured on the 7th day after insertion of each splint. The four experimental occlusal conditions were found to have a significant effect on the tapping point distribution. The complete elimination of the protrusive tooth contact caused an anterior tapping point location and an increase in the tapping point area. The former tendency was found to be independent of the presence of the retrusive tooth contact. In conclusion, it was suggested that the protrusive tooth contact plays a significant role in maintaining the consistency and stability of the tapping point.