EMG, bite force and its relation to craniofascial characteristics

The relationship between electromyographic (EMG) activity and bite force varying in the vertical dimension (VD) allowed the determination of the optimum VD, defined as the position in which the masseter muscle develops the maximum force with minimum EMG activity. The craniofascial characteristics of each of 8 subjects was analysed in order to explain the different optimal vertical dimensions (13-21 mm) obtained. Gonion angle was the most important factor. The results suggest that when the mandible is projected forwards and the gonion angle is smaller, the optimum VD is reached nearer to the occlusal vertical dimension. On the contrary, when the mandible is projected backwards and the gonion angle is larger, the optimum VD is reached further from the occlusal vertical dimension.