The Profile of Occluding Strength and Masseter Muscular EMG Power Spectra during Short Time Clenching

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In order to clarify whether it is possible to objectively evaluate masticatory muscular Function, the masseter activity during clenching were analyzed and the following results were obtained.1. After recording the masseter activity by an EMG of healthy subjects clenching with 80% of maximum clenching for 10 seconds, a program was created that is able to display on the computer both the original wave pattern and the power spectra of the muscular activity.2. 80% clenching by healthy subjects for 10 seconds were performed under two types of conditions (80%MVF : feedback from occlusal force and 80%MVC : feedback from integral values of masseter activities) and the masseter activity and occlusal force were recorded. The 10 seconds of clenching were divided into 5 sections of 2 seconds. Setting the first section as 100% the relative values of MPF values and integral values of masseter muscular activity and occlusal force of the second to fifth section in relation to the first section were in … More vestigated. As a result the relative values of MPF values showed significant changes with time for both 80%MVF and 80%MVC. However no significant differences between 80%MVF and 80%MVC were found. From these results it was concluded that during a short time clenching a certain amount of occlusal force and muscular activities could be generated, and the EMG power spectra of masseter muscle were not affected by various conditions of recording.3. Healthy subjects were asked to perform 80%MVC for 10 seconds and the masseter muscular activities and occlusal force were recorded. 10 seconds were divided into 5 sections of 2 seconds, and by setting the first section as 100% the relative values of occlusal force and MPF values for the second through fifth sections were investigated. As a result the relative values of occlusal force were close to 100% for all sections and changes along time were not observed. On the other hand the relative values of MPF values decreased gradually and a significant change along time was observed. From these results it was concluded that during short time clenching the occlusal force was maintained at a certain level and the MPF values of the masseter EMG power spectra decreased significantly along time. Less