Human jaw-elevator muscle activity and food comminution in the dentate and edentulous state.

Masseter and temporal surface electromyograms were obtained from seven dentate subjects and six complete-denture wearers during mastication, maximal voluntary clenching and measurements of bite force. The participants chewed two artificial test foods with different textures. The dentate subjects comminuted both foods much better than the denture wearers. In both groups, the softer food was comminuted better than the firmer food. The differences in particle-size reduction originated largely from differences in the numbers of particles fragmented per chewing stroke. The rhythm of mandibular movement was unaffected by food texture and dental state. No significant differences in the duration of bursts of electric muscle activity were found between either group. Peak amplitudes of activity during mastication and maximal voluntary clenching were more than twice as large in the dentate subjects as in the denture wearers. In both groups, chewing the softer food was associated with lower peaks of activity than with the firmer food. The peak amplitudes were weakly related to the reduction in particle size. In both groups, the peak forces determined from electromyographic activity were larger than the estimated forces required for fragmenting the particles between the teeth.