The Influence of Craniofacial Form on Bite Force and EMG Activity of Masticatory Muscles. III-1. Vertical Clenching of Normal Face Group.

To analyze the influence of craniofacial morphology on the functions of stomatognathic system, dentulous subjects in the normal face group were selected and had been engaged in vertical clenching to measure the magnitude and direction of bite force as well as the EMG activity of masticatory muscles. The correlation was studied among them.The results were as follows:1. The correlation curve of temporal muscle was hyperbolic. The correlation curves of masseter muscle and medial pterygoid muscle were linear.2. The ratio of the EMG activity of the increasing part was equal to or higher than that of the holding part at 25-100%MC.3. A significant correlation was observed between θ' and 4 angle measurements. The correlation of 13 items of the craniofacial measurements and direction of bite force was investigated with the EMG activity per 1kgf. A significant correlation was observed between the EMG activity per 1kgf and several items of craniofacial measurements.