Normalized EMG Linear Envelope Analysis of Masticatory Muscle Activity Patterns for the Preferred and Nonpreferred Side during Gum Chewing

Abstract

The purpose of this study was to investigate the differences in coordination patterns of elevator muscles during gum chewing on the preferred and nonpreferred sides (PRC and NPRC) using normalized electromyographic linear envelopes (EMG LE_s). Experimental tasks were carried out utilizing two kinds of gum with different hardnesses and ten normal subjects. EMG LEs normalized with respect to EMG amplitude and stroke were generated from surface EMG signals of bilateral anterior temporal, posterior temporal and masseter muscles (WTa, NWTa, WTp, NWTp, WM and NWM) and incisal point movement of the mandible. Differences in coordination patterns of EMG LEs for masticatory muscles between PRC and NPRC on different gum hardnesses were evaluated by the cluster analysis.
On the soft gum, there was a high phasic similarity between EMG LEs of WM and NWTa during NPRC. NWM had similar phasic characteristics for another muscle during NPRC. On the hard gum, differences in muscle coordination patterns between PRC and NPRC were basically the same as those for soft gum chewing. From the viewpoint of chewing difficulty, there was no change in coordination patterns among WTp, NWTp and NWM between soft and hard gum on PRC in comparison with that between PRC and NPRC on soft gum.