Influences of ovariectomy and orchiectomy on the remodeling of mandibular condyle in mice.

Ovariectomy (OVX) and orchiectomy (ORX) are well known to increase bone turnover; however, the influences on condylar remodeling are not fully understood. The purpose of this study was to examine histological changes of the mandibular condyles in OVX and ORX mice in comparison to the femora. Eighty 8-week-old mice were used in this study. In each of the experimental and control groups, five mice were sacrificed 2, 4, 8, and 12 weeks after surgery for OVX and ORX. Histological changes of the mandibular condyle were studied in comparison to the femur, which is liable to undergo the influences of OVX and ORX. The number of TRAP-positive cells and the thickness of articular cartilage layer were also quantified. TRAP-positive cells in the condylar head of OVX and ORX mice exhibited the most prominent increase 4 weeks after the surgery and approached the control levels at the later experimental stages. Trabecular bone volume in the condyle of the OVX and ORX mice also decreased, although the rate was less than in the femora. It is shown that influences of OVX on the remodeling of femora appear earlier than those of ORX, whereas OVX and ORX affect the remodeling of condyle during the same growth period. It is also demonstrated that the influences of OVX and ORX are less in the condyle than in the femora. These findings emphasize that the influences of OVX and ORX on bone remodeling are varied by sexual difference and the type of bones.