Unusual postero-inferior condylar movements that depend on the position of occlusal contact during fictive mastication in XXXX .

@entity1 @entity7871 @entity95 @entity2956
OBJECTIVE: The mandible can be modelled as a triangular plate supported at two joints and the point of occlusion. The mandible is stable if the vector of the jaw-closing muscle forces lies within the triangle of support. If this vector lies outside of the triangle of support, one of the three contact points will tend to separate as the mandible rotates around a line connecting the other two points. Here, we examined whether postero-inferior condylar movements (Pi-Cm) due to mandibular rotation may occur during fictive mastication in anaesthetized @entity95 . METHODS: EMG activities of the @entity7871 ( @entity7871 ) and lateral pterygoid (LP) muscles and movements of the condyle and incisal points were recorded. Condylar movements in the sagittal plane were recorded using a high speed CCD camera. RESULTS: Pi-Cm were observed on the working side during occlusal phase in half of the @entity95 (altered-movement group), if the biting point was restricted at the posterior most tooth (M3) on the working side using a metal biting plate. Pi-Cm appeared in the period between the estimated maximum force of the @entity7871 and the LP during late occlusal phase. The @entity7871 EMG ratio between the working and balancing sides in the altered-movement group was significantly less than that in the unaltered-movement group. CONCLUSION: Since the space lying between the condyle and the articular eminence expanded during the Pi-Cm, it is likely that the posterior band of the articular disc tended to slip anteriorly. The clinical significance of the Pi-Cm is discussed concerning the anterior dislocation of the disc in @entity1 with @entity2956 .
