Electromyographic study of the activity of jaw depressor muscles before initiation of opening movements

Abstract

We attempted to clarify the primary factors determining the timing of initial electromyographic discharges of the jaw depressor muscles (EMG-onset) by examining how to change EMG-onset by varying the duration of the open-close movement or occlusal force using the open-close-clench cycle (OCC). We also considered the effect of tooth contact and mechanoreceptors in the periodontal tissues. On both normal dentate and edentulous subjects, EMG-onset preceded initiation of opening during OCC. In normal subjects, mean masseter muscle activity associated with occlusal force was found to have significant correlation with EMG-onset. However, in open-close movement without tooth contact, EMG-onset tended to delay initiation of opening movement.