下顎運動の加齢による変化に関する研究 第２報 側方滑走運動の解析

Abstract

Mandibular movements as a whole have not been sufficiently investigated, due to the great difficulty of recording them. In order to clarify those features in three-dimensions, we measured 62 cases whose ages ranged from 20 to 79, and whose dentitions were either complete or nearly so, and whose intercuspal positions were firm. Part 1 of this study revealed the differrent types of sagittal movements seen among various age groups. We then investigated lateral excursions, gaining the following results: 1) no statistical difference could be found in the movement direction at incisor, canine or first molar either on the working or non-working sides, among any of the age groups studied; 2) the inclination of the condylar path tended to lessen with advancing age; 3) the sagittal inclination of the second molar path on the non-working side tended to be gentler in subjects 60 years and older than in younger subjects, which would reflect the previous result, and 4) there was no statistical difference in path-length of the working-side condyle among the various age groups. These results showed that the posterior guidance on the non-working side tended to change with age, even in subjects with nearly-complete dentition, probably due to the morphological changes of the temporomandibular joint.