Clearly, there was an influence of psychological factors, such as stress, on TMD, and such factors were considered to play important roles in its etiology, progression, and treatment. The results of this study suggest that well-controlled studies of TMD are necessary.

Comparison between subjects who were mailed the questionnaire and questionnaires available for analysis Subjects who were mailed the questionnaire Questionnaires available for analysis Without: Without the retainers on the contralateral side With: With the retainers on the contralateral side A questionnaire

The purpose of this study was to investigate mandibular position sense with four different jaw openings (5,10,15and20mm 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). Immidiately 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 statisticaly analyzed. 1. In the closing approach, perceived mandibular positions were become lower, but in the opening approach, significantly higher than reference positions (5mm: p<0.00001, 10mm: p< 0.05, 15mm: p<0.025, 20mm: p<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 (5mm: p< 0.001, 15mm: p<0.025). 3. On 5mm reference position, variance of data was significantly lower than the others. On 10mm 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.

On 5 mm reference position, however, it was no significant.2. On 5 mm reference position, variance of data was significantly lower than the others (P< 0.01). 3.In maximum open (C5) of five conditions, variance of data was significantly greater than the others (P<0.01).4. It was suggested that mandibular position sense was affected by mandibular spatical vertical position and that the muscle spindle plays an important role in neuronal mechanism of controlling mandibular position.