Effect of Aging on Bone Remodeling in Canine Mandibular Condyle

Abstract

Previous research indicates that overall, bone turnover decreases with age. The effects of aging on the remodeling of the mandibular condyle have not been studied. As part of the temporomandibular joint, the mandibular condyle (MC) is exposed to a unique pattern of loading. As such, data obtained from studies of other bones may not be applicable to accurately explain the behavior of trabecular bone of the mandibular condyle and its relationship to aging. Recent research has led to the finding that cortical bone turnover in the mandible is much higher than that seen in tibia, and that both sites decline with age. The purpose of this study was to histomorphometrically quantify the effects of aging on the bone remodeling of the canine MC, and to determine whether site-specific differences due to age occur in the dynamic and static parameters between MC and tibial condyle (TC). Fluorochrome labels were used to mark sites of bone formation in ten old and five young dogs. Specimens were obtained from one MC and one TC for each dog and were prepared for analysis of static and dynamic histomorphometric indices. Mineral apposition and bone formation were totally absent in the old group, as shown by the lack of fluorochrome labels. In the young group, they were significantly higher in the MC than in the TC (p < 0.01). Aging resulted in a significant increase of volume density of the subchondral bone (p < 0.05). Trabecular bone volume was not significantly affected by age in the samples studied. The results indicate that bone remodeling is markedly higher in MC than in the TC in young dogs. With aging, it declines to zero in both sites. Whether the loss of remodeling activity in these elderly animals indicates that they are fully adapted to their mechanical environment or that they have lost the intrinsic ability to remodel, remains to be determined.