Verification of working hypothesis on the mechanism of occurrence of the temporomadibular disorder in the experimental animal models

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The results of the present study are summarized as follows ;1) Rabbit is useful for studying the mechanism of occurrence of the temporomadibular disorder. Because we can control the jaw movement pattern by electrical stimulation of the different portion in the masticatory cortical area (MCA). When stimulated in the medial part of the MCA,chopper-type jaw movement was induced and when stimulated in the lateral part of the MCA,grinding-type jaw movement was induced.2) In combination with jaw movements, we recorded video movie of the movement of the articular disk by removing the roof of the glenoid fossa. It appeared that removing the roof of the glenoid fossa did not seriously affect the movements of the jaw and disk. However we could not analysis in quantity the movement of the disk in relation to the jaw movement and the EMG activities of the masticatory muscles during grinding-type jaw movement induced by stimulation of the lateral part of the MCA.Because of insufficient time-resolution of the video movies and disturbed jaw movement record by vibration of jaw tracking equipment.3) Electrical stimulation of the superior head of the lateral pterygoid muscle (SUP) did not induce the positional change of the disk relative to the condyle but the stimulation of the zygomato-madibular muscle produced marked displacement of the disk. This suggests that the ztgomato-madibular muscle may play important role in the control of the movement of the disk.