Analysis of jaw movements and masticatory muscle activity.

This paper describes software developed to analyze the temporal and spatial aspects of jaw movements, the speed, direction and magnitude of these movements in three dimensions, and the associated electromyograms (EMGs) of the masticatory muscles. Data from a subject chewing gum illustrates the software application. Manipulations of the stored digitized data are described. Temporal aspects of each chewing cycle are defined by specified delimiters for the beginning and ending of jaw opening and closing; spatial aspects are quantified by measurements derived from movement trajectories; and peak and mean velocities are derived from the velocity profiles. EMGs are digitized, rectified, averaged and referenced to jaw movement. Onset latencies, burst durations, rise times to peak activity, time of occurrence of peak activity, and amplitudes of peak and mean activities are measured from the EMGs. This detailed kinematic/EMG analysis provides previously inaccessible information about jaw muscles and the movements they control.