顎関節形態および前歯部被蓋状態が前方滑走運動に及ぼす影響

Abstract

Maxillary central incisors are important as a dental factor of protrusive excursion. However, most orthodontists decide upon the relationship of maxillary central incisors without considering protrusive excursion in order to improve the function of mandibular movements and esthetics of facial profile. In the present study, to obtain data on the effects of changed incisal guidance on protrusive excursion, fifteen adult male subjects with normal occlusion and another fifteen adult male subjects with maxillary protrusion were selected, and records of the temporomandibular joint morphology and protrusive excursion were made using cephalometric laminagraph. In addition, data of protrusive excursion were collected when incisal guidance was experimentally changed on subjects with maxillary protrusion. Using this information, the effects of the temporomandibular joint morphology and incisal guidance on protrusive excursion were examined. The following results were obtained. 1. In cephalometric laminagraph, the depth of cut through the center of the condyle was a very effective method in which to examine the temporomandibular joint morphology and condyle path. 2. There was no significant difference in the temporomandibular joint morphology between the subjects with normal occlusion and those with maxillary protrusion. 3. There were significant differences in the condyle path from the intercuspal occlusal position to the edge-to-edge occlusal position between the subjects with normal occlusion and those with maxillary protrusion, and values of the angle and distance were bigger in the subjects with maxillary protrusion than in those with normal occlusion. 4. There was a correlation between the condyle path from the intercuspal occlusal position to the most anterior occlusal position and the inclination of articular eminence in the subjects with normal occlusion or with maxillary protrusion. 5. There were no correlations between the condyle path from the intercuspal occlusal position to the edge-to-edge occlusal position, and the inclinations of the articular eminence and lingual surface of maxillary central incisor, or between the inclination of the lingual surface of maxillary central incisor and the inclination of articular eminence, in the subjects with normal occlusion or with maxillary protrusion. 6. The steeper the incisal guidance was made, the steeper became the condyle path when the incisal guidance was experimentally changed. The foregoing results suggest that jaw movements alter when the incisal guidance is changed by orthodontic treatment. Therefore, orthodontists must pay attention to jaw movements and temporomandibular morphology.