Time-series analyses of mandibular and perioral soft tissue movements during mastication

Masticatory movements are rhythmically repeated and coordinated movements of the jaw, tongue and facial muscles. Thus, we considered that the elucidation of movements that are specific to perioral soft tissue, as a result of perioral facial muscle activities, should be useful for evaluation of the smoothness of masticatory movements. The aim of this study was to evaluate the smoothness of masticatory movements from the component of movements that are specific to perioral soft tissue during mastication by the application of time-series analysis. The subjects were 15 healthy persons with complete natural dentition. The experimental food used for mastication in this study was sufficiently softened chewing gum. The results showed that the component of movements that are specific to perioral soft tissue during mastication are the equal repetition spatially and stable movements temporally, and that these movements have the same accurate rhythm as that of mandibular movements and cooperate with mandibular movements temporally. Moreover, the results suggested, from the viewpoint of kinematics, that the innervation of the central pattern generator was concerned with the neural basis of rhythm generation of perioral facial muscles. Therefore, the component of movements that are specific to perioral soft tissue during mastication is useful for evaluation of the smoothness of masticatory movements.