Effect of Bite Position on Masticatory Muscle Activity during Tooth Bite Task Using Novel Standardized Bite Device

Abstract

To help elderly adults maintain good oral function, standardized oral motor training that considers missing posterior teeth needs to be established. This study aimed to investigate effect of bite position on masticatory muscle activity during tooth bite task using novel standardized bite device（BDs）. Twenty-five healthy male volunteers were classified by age into two groups: Young Adults（YA）group（n=12）and Pre-Elderly（PE）group（n=13）. Experimental design included three types of BDs（High-Force, Low-Force, and Dummy）, two age groups（YA and PE）, and two bite positions（premolar and molar）. For training, participants performed biting task 50-times on six types of bite training（three types of BDs×two bite positions）in random order. During training, electromyographic（EMG）activities were recorded from both masseter and temporalis muscles. Working / balancing side activity ratio（W/B ratio）of the masseter and temporalis muscles were calculated. The coefficient of variation（CV）from the relative ratio of the EMG RMS amplitude during each bite task in each channel was calculated. For all BDs, CV for EMG activities in both masseter and temporalis muscles were not significantly different by age or bite position. For High-Force and Low-Force BDs, W/B ratio of EMG activities in temporalis muscle were significantly higher than those in masseter muscle. Present study may suggest that our newly developed BD with built-in plate spring affected EMG activity in temporalis muscle on working side, but not in masseter or temporalis muscles on balancing side, regardless of age or bite position within the posterior teeth.