Coordinated movements of the mandibular condyle and the articular disk in decreased occlusal vertical dimension in rabbit.

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In decreased occlusal vertical dimension, jaw movement and electromyogram activity were recorded. And we studied the relation between movements of the mandibular condyle and alteration of occlusion. The experiment which after cut the articular tubercle visualizes stress as mandibular condyle movement in the articular tubercle direction was conducted as preliminary step for investigate influence of cut the molar region. In tubercle cutting side was working side case, modification in the movement caused as project forward in occlusal phase. Additionally, trajectory of motion shifted in an anterosuperior direction in the period when activity of the jaw closing muscle does not occur as opening phase. This shows that articular tubercle received stress by resting tension of jaw closing muscle and elastic force of skin. Moreover when cut the molar region on the ipsilateral side, project forward movement in occlusal phase and trajectory of motion forward shift increased. This suggest that stress for articular tubercle increased.Pathogenesis of temporomandibular disorder is considered multifactor, for example, occlusal abnormality, increase in muscle tone, lifestyle habit, mental stress. However, abnormal stress loading and abnormal jaw movement are essential for morphological defect of temporomandibular joint and abnormal position of articular disk.This studies are expected to play an important role in revealing the pathogenesis of anterior dislocation of articular disk.