Some aspects of mandibular movement: acceleration and horizontal distortion.

Two aspects of mandibular movements were measured. Using a small accelerometer, peak peripheral acceleration on opening the mouth was found to average 2.54 +/- 0.4 G. Average angular velocities for both opening and closing actions were similar at approximately 1.9 rad/s; and the average maximum angular velocities were 4.63 +/- 1.45 rad/s during opening, and 3.24 +/- 1.15 rad/s during closing. Medial distortion of the mandible in the horizontal plane was measured. It was shown that medial approximation of the two halves of the mandible occurs on opening the mouth, protrusion of the tongue, protrusion of the mandible and when medially directed forces are applied to the ramus of the mandible. Divergence of the two sides occurs with laterally directed forces. During speech, complex medial distortion involving divergence and convergence occurs.