Studies on Mandibular Closing Position in Opening and Closing Movements without Tooth Contact

Abstract

We studied mandibular closing positions during habitual opening and closing movements with and without contact of the teeth in nineteen normal dentate subjects, using the Mandibular Kinesiograph (Model K-6, Myo-tronics).
      There was more variation in the closest position without tooth contact (CP) between subjects and between trials than in the closest position tapping points with tooth contact (TP). Decreasing the velocity of mandibular movement significantly shifted CP to the anterior. A wider opening distance produced greater lateral deviation in CP. Also the variation between consecutive jaw movements was less in the upright position than when the subject was inclined to 45°or in the supine position. CP showed a significant shift to the anterior during opening and closing movements when the subject was inclined back 45°and in the supine position. This was especially noticeable when the opening distance was wide. This suggests that the upright position is best for registration of mandibular position.
      Five subjects with unstable intercuspal position and abnormal jaw trajectory movements had larger variations in CP and TP than did the normal subjects. This implies that CP and TP are closely related to oral function.