Computer-based assessment of habitual mastication

A computer-based system to assess mandibular movements and EMG masseter and temporal muscle activity during habitual mastication was applied to 12 healthy subjects and the chewing performance was tested with a standardized bolus of crisp bread. A Siemens Sirognatograph instrument was used to record mandibular movements while EMG signals were recorded with surface silver-silver electrodes. Software provided data of single chewing cycles in space and versus time, of mean mandibular displacement during opening and closing, mean velocity, and EMG activity. Clockwise and counterclockwise cycles were computed separately. The data obtained allow the following conclusions: Habitual mastication is a rhythmic event with different envelopes of motion that alternate characteristically in each subject. Each chewing cycle accomplishes several tasks but, depending on its envelope, is probably more oriented to a specific performance. A mean chewing cycle can be constructed for each individual. Its pattern depends on the distribution of different envelopes of motion that alternate during the masticatory sequence. During closure, a prevalently isotonic and a prevalently isometric phase of muscle contraction can be distinguished. Mean movement and EMG data for the whole group are not distributed at random, but according to a typical pattern. The system seems to be finalized to a well-balanced function and distribution of loads.