Effect of the location of chewing on facial and jaw muscles activity and the mandibular movement.

This paper evaluates the influence of the location of chewing on facial and jaw muscles' activity and mandibular movements. Ten subjects with complete dentition performed following chewing sequences; 1) right side chewing (unilateral location-unspecified chewing); 2) chewing on right molars; 3) chewing on right premolars; and 4) chewing on anterior teeth. Bilateral activities of upper lip, cheek, masseter (anterior, middle and posterior parts), and anterior bellies of digastrics were recorded by surface electromyography. Mandibular movements were simultaneously recorded by electrognathography. Chewing on anterior teeth showed smaller masseteric activity in posterior part, smaller envelope of motion, and lower velocity of both opening and closing than unilateral location-unspecified chewing and chewing on right molars. Chewing on premolars showed smaller envelope of motion than chewing on molars. No significant difference was found between unilateral location-unspecified chewing and chewing on premolars or molars.