[Kinesiological and electromyographical study on masticatory movement. I-3. The changes in the jaw position corresponding to the muscular discharge activities of masticatory muscles during the process of mastication].

For the purpose of clarifying the aspests of masticatory movement and producing the clinically index of jaw movable analysis, the phasic masticatory movement andelectric discharge activity of masticatory muscle of natural dentitions were recorded simultaneously during the mastication of peanuts ham and takuan, using the Saphon visitrainer which is an analytical equipment for the jaw movement and the polygraph (RM-6000). As a result of this study, following conclusions were obtained. 1. The correlation coefficient was negative in each masticatory muscle and each ofthe three different types of food at the time when muscular activities started and when they reached a maximum; and WT became significantly smaller than other masticatory muscles. 2. As for the confidence interval of regression coefficient, that of the masticatory muscle on the working side (WT, WM) became smaller than that of the masticatory muscle on the balancing side (BT, BM) when the muscular activities for masticating the three defferent types of food atarted and when they reached a maximum. 3. It has been estimated that the quantitative indication of the changes in the mandibular position by the correlation coefficient and the confidence interval of regression coefficient will serve as an index of masticatory functions.