[Mandibular position sense during open-close movement]

The purpose of this study was to investigate mandibular position sense with four different jaw openings (5, 10, 15 and 20 mm from intercuspal position) during open-close movements. Eight subjects memorized the reference positions with monitoring their spatial vertical jaw positions using a Mandibular Kinesiograph (M.K.G., K-5). Immediately after memorizing one of those positions, they were required twenty times open-close movements; that is, approaching the memorized position from superior (opening approach) or from inferior position (closing approach) and receding were repeated. Vertical distances from intercuspal position at lower incisal teeth were recorded by MKG and statistically analyzed. 1. In the closing approach, perceived mandibular positions were become lower, but in the opening approach, significantly higher than reference positions (5 mm : p less than 0.00001, 10 mm : p less than 0.05, 15 mm : p less than 0.025, 20 mm : p less than 0.005). 2. In the closing approach, the inclination of regression lines shows significantly the estimated decrement to come near closed position throughout twenty experimental sequences (5 mm : p less than 0.001, 15 mm : p less than 0.025). 3. On 5 mm reference position, variance of data was significantly lower than the others. On 10 mm with opening approach, it was the highest of all. 4. It was suggested that mandibular position sense was affected by mandibular spatial vertical position and direction of approaching during jaw movements, and that neuronal mechanism of controlling mandibular positions and movements were more excellent near tooth contact.