三次元こう合力に基づく下顎位とそしゃく筋活動の関係に関する研究

Abstract

The purpose of this study was to examine the relationship between jaw position and masticatory muscle activities during static bite situation. The subjects were 4 males and 1female. EMG activities were registered bilaterally from the masseter muscle (MAS), anterior temporal muscle (AT) and posterior temporal muscle (PT) in different jaw positions anteroposteriorly. During EMG registration, bite force was regulated both in magnitude and direction with visual biofeedback by means of a three-dimensional bite force measuring device. The relative activation pattern of the muscles during bites in specific directions was consistent irrespective of jaw position. During bites in a specific direction at a determined force, MAS activity increased as the jaw position was changed anteriorly, while AT and PT activities increased as the position was changed posteriorly. The difference between activities generated in different directions was dependent on jaw position in AT and PT, but not in MAS. The difference between the activities generated at different bite forces was dependent on jaw position in MAS and AT, but not in PT. It was suggested that these characteristics of muscle activity as changes of jaw position might be closely related to the shape and spacial location of muscles.