2012 Volume 24 Issue 3 Pages 157-167
Objective: In cases where an articular disk malposition such as anterior disk displacement is caused by a failure of coordinated movements of the mandibular condyle and articular disk, elucidation of the coordinating mechanism of the mandibular condyle and articular disk movements may help clarify the pathogenesis of the anterior disk displacement. The purpose of this study was not to observe static positions of the mandibular condyle and the articular disk but to clarify the coordinating mechanism between the mandibular condyle and articular disk by investigating the movements of the mandibular condyle and articular disk during masticatory movements.
Method: EMG activities of the masseter muscle were simultaneously recorded with movements of the condyle and disk as well as the incisor point during masticatory-like jaw movements induced by electrical stimulation of the cortical masticatory area of anesthetized rabbits.
Conclusion: The trajectory of the anterior point of the mandibular condyle was localized to a vertically small region and straight pathway. It has been suggested that the mandibular condyle moves across the articular disk from the articular tubercle and maintains a stable relation with the articular disk. The articular disk moved along the articular tubercle during masticatory movements but slight forward-projecting movements were seen in an early occlusal phase. The forward-projecting movements occurred simultaneously with the peak of the masseter muscle contraction force, suggesting that the articular disk received compressive force from the mandibular condyle. However, significant deformation of the articular disk was not observed.
