Measure of bite force and occlusal contact area before and after bilateral sagittal split ramus osteotomy of the mandible using a new pressure-sensitive device: a preliminary report.

Seven women patients at Tufts University School of Dental Medicine were evaluated for the subjective symptoms of a myofascial pain dysfunction. Each patient was evaluated by an occlusal analysis of the T-Scan computer to determine posterior disclusion time during excursive movements, and EMG analysis of the masseter and temporalis muscles. Each patient was then treated occlusally by developing immediate complete anterior guidance. This adjustment process involved the removal of all lateral and protrusive interferences prior to habitual closure adjustments. No attempt was made to retrude the mandible in centric relation, and splints were not used to deprogram the musculature before adjustment. In this study, protrusive movements and interferences were not examined, and there was no control group. Posttreatment EMG and T-Scan computer analyses revealed that by shortening disclusion times to less than 0.5 second in any lateral excursions, muscle function returned to normal in all seven patients in approximately 1 month's time. A direct correlation seemed to exist between contractile muscle activity and disclusion time. Lengthy disclusion time leads to excessive muscle activity that introduces spasm and fatigue of the masseter and temporal muscles. These results indicated that a partial explanation of the etiology of MPDS may be the time the molars and nonworking premolars remain in contact during excursive movements--a phenomenon termed "disclusion time."

Electromyographic and computer analyses of patients suffering from chronic myofascial pain-dysfunction syndrome: before and after treatment with immediate complete anterior guidance development.

Statement of Problem. Quantitative measures of occlusal contacts are of paramount importance in the study of chewing dysfunction. A tool is needed to identify and quantify occlusal parameters without occlusal interference caused by the technique of analysis. Purpose. This laboratory simulation study compared occlusal contacts constructed from 3-dimensional images of dental casts and interocclusal records with contacts found by use of conventional methods. Material and Methods. Dental casts of 10 completely dentate adults were mounted in a semi-adjustable Denar articulator. Maximum intercuspal contacts were marked on the casts using red film. Intercuspal records made with an experimental vinyl polysiloxane impression material recorded maximum intercuspation. Three-dimensional virtual models of the casts and interocclusal records were made using custom software and an optical scanner. Contacts were calculated between virtual casts aligned manually (CM), aligned with interocclusal records scanned seated on the mandibular casts (C1) or scanned independently (C2), and directly from virtual interocclusal records (IR). Sensitivity and specificity calculations used the marked contacts as the standard. Contact parameters were compared between method pairs. Statistical comparisons used analysis of variance and the Tukey-Kramer post hoc test ( P = Results. Sensitivities (range 0.76-0.89) did not differ significantly among the 4 methods ( P =.14); however, specificities (range 0.89-0.98) were significantly lower for IR ( P =.0001). Contact parameters of methods CM, C1, and C2 differed significantly from those of method IR ( P CM/C1 = CM/C2 > C2/IR > CM/IR > C1/IR, where ">" means "closer than." Conclusion. Within the limits of this study, occlusal contacts calculated from aligned virtual casts accurately reproduce articulator contacts. (J Prosthet Dent 2002;88:622-30.)

Comparing maximum intercuspal contacts of virtual dental patients and mounted dental casts.

The contact area during habitual biting can vary according to the activity of the jaw musculature. Forceful masticatory muscle activity may also induce deformations of the dento-alveolar tissues and the supporting skeleton, yielding various tooth loads despite an apparently even distribution of tooth contacts. To investigate this variability, we measured bite forces simultaneously at multiple dental sites during maximum-effort clenching tasks. In each of four healthy adults with complete natural dentitions, four strain-gauge transducers in the right side of an acrylic maxillary appliance occluded with the lower canine, second premolar, and first and second molars. These, and matching contralateral contacts, were balanced by means of articulating paper and a force monitor (type F appliance). Bite forces were recorded when the subjects, without visual feedback, clenched maximally on the appliance. Similar recordings were made when contralateral molar and all contralateral contacts were removed (type R and t...

The Association Among Occlusal Contacts, Clenching Effort, and Bite Force Distribution in Man

Statement Of Problem. The controversy continues regarding the efficacy of several commercially available devices that are used as aids in the diagnosis of occlusal abnormalities. Purpose. This article reviews the reliability, validity, and utility of instruments that claim to detect occlusal interferences and abnormal vertical dimension of occlusion. Material And Methods. Data, opinions, and technical information from 37 published articles were reviewed. Evidence for method reliability, validity, and utility was assessed. Results. Although 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 overclosure. Conclusion. None 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. (J Prosthet Dent 2000;83:83-9.)

W L Maness

Papers

Computerized occlusal analysis: a new technology.