The effect of ovariectomy on the temporomandibular joints of growing rats.

PURPOSE: This investigation studied the effects of ovariectomy, on the temporomandibular joints (TMJ) of young rats.
MATERIALS AND METHODS: Four-week-old female Wistar rats were ovariectomized and killed at the intervals of 1, 2, 4, and 8 weeks postoperatively. Histomorphometric study of the TMJ was performed in a synchronous manner with an age-matched sham-operated control group. The serum levels of estrogen, calcitonin, and C-terminus parathyroid hormone were also determined.
RESULTS: In the sham-operated control group, the serum levels of estrogen and calcitonin increased with age. An increase of the bone volume, with a concomitant increase of the osteoid surface, was observed at 12 weeks. Thickness of the articular soft tissue was decreased with increasing age. In the ovariectomized animals, serum estrogen was not detected during the experiment. A biphasic change in the parathyroid hormone level, with decreases at 1 and 2 weeks after the ovariectomy and increases at 4 and 8 weeks postoperatively, was observed, whereas a constant value was noted in the calcitonin level. Thickness of the articular soft tissue was increased in the anterior and central portions of the condyle at 1, 2, and 4 weeks after the ovariectomy, whereas no appreciable changes were observed in the posterior portion. The bone volume was decreased during the experiment, particularly in the posterior portion. An osteophyte in the anterior region was also observed 8 weeks postoperatively.
CONCLUSIONS: Estrogen deficiency in rats during puberty predisposes to alterations of the TMJ through changes in serum calcitonin and parathyroid hormone levels.