Effect of Varying Biting Position on Relative Jaw Muscle EMG (Electromyography) Activity

摘要

Several numerical models that abstractly represent the masticatory system have been proposed. These models predict the distribution of forces among the muscles and the reaction force in the joint based on a given occlusal load. Little information is available regarding the accuracy of model predictions. The purpose of this study was to compare the pattern of model predicted jaw muscle forces with the pattern of electromyography (EMG) activity from those same muscles as constant bite force was moved around the dental arch. EMG recordings were made bilaterally from the anterior and posterior temporalis and masseter muscles of ten subjects while they bit with constant force on a transducer at seven positions around the dental arch. Both predicted model forces and EMG data were converted to standard scores allowing comparison of patterns at the various biting positions. EMG activity patterns for the masseter showed symmetrically decreasing activity on the ipsilateral and contralateral sides from a high point of activity at the incisors. Model predictions for masseter suggested bilateral decreasing activity from the incisors posteriorly, however, activity on the ipsilateral side was considerably higher than corresponding positions on the contralateral side. This model asymmetry was in contrast to the symmetry in corresponding biting positions observed in the EMG activity patterns.