[Study of objective assessment for pathways in areas of intercuspal position during masticatory movements]

Masicatory function is the result of a highly complicated neuromuscular activity which coordinates in stomatognathie system. Functional directions of masticatory cycles in areas of intercuspal position (IP) were objectively evaluated on each stroke obtained through the Sirognathography Analyzing System (S. G. G./A. S.; Siemens, W. Germany). Twenty seven dantate subjects were selected at random from students and staff members of Kanagawa Dental College. A piece of chewing gum was given to each subject to masticate it for a minute on one side and on the other side respectively. A total of masticatory cycles were successively recorded into S. G. G./A. S.. A statistical analysis, the equal probability for ellipstical variations, was made on the angular measurements from opening and closing phases of each cycle within 3 mm from onset and terminus in areas of IP during masticatory movements. Four characteristic features of angular measurements are presented, namely, subjects who showed different types in position and forms by plotted angles within 80% of total amounts. The following results were obtained from this study. 1. Functional directions of masticatory cycles are clearly recognized in areas of IP from opening and closing phases during masticatory movements. 2. An application of the equal probability for ellipstical variations seems to be efficient for the functional analysis of masticatory cycles. 3. A classification of different types of plotted angles contributes to become a basis for diagnosis of masticatory function and occlusion.