[Experimental studies concerning the effect of food consistency on masticatory movement in man]

The purpose of this study is to investigate the relationship of food consistency to patterns of mandibular movement and jaw muscle activity during mastication in adults with normal dentitions. Ten young people who ranged in age from 23 to 26 were studied. Specially made chewing gums of 3 graded consistencies (4.4 x 10(2), 1.4 x 10(4), 1.3 x 10(5) poise), not contain any additive like sugar and flavor, were used as test foods. Mandibular movements were recorded and analyzed using a Mandibular Kinesiograph (Myotronics Research Co.) during chewing of the 3 grades of chewing gums for 40 strokes. Surface EMG signals were also recorded from the bilateral masseteric and anterior temporal muscles. Displacement and velocity of jaw movement, duration of each phase, and amount of EMG activity were then statistically compared among chewing trials of the 3 grades of chewing gums with two way analysis of variance. The results were as followed. With the increase of consistency of chewing gum; 1. Maximal vertical, antero-posterior and lateral displacements were significantly increased (p less than 0.01). 2. Maximal opening and closing velocities were significantly increased (p less than 0.01). 3. Opening phase time was significantly increased while occlusal phase time was significantly decreased (p less than 0.01). Cycle time and closing phase time were about constantly. 4. Burst duration, interval and cycle time were about constantly. 5. Burst activity were significantly increased (p less than 0.01). 6. Burst co-ordination pattern was about constantly.