Effect of estrogen replacement on temporomandibular joint remodeling in ovariectomized rats

The investigation was performed to elucidate the effect of estrogen on the temporomandibular joint (TMJ) and to evaluate the therapeutic effect of 17beta-estradiol replacement in growing rats.

Thirty 4-week-old female albino Wistar rats were divided into 3 groups. Ten rats were ovariectomized followed by intramuscular administration of 17beta-estradiol for hormone replacement (OVX + E2), 10 were sham operated (CTL), and 10 were ovariectomized without hormone replacement (OVX). Five rats from each group were killed at 1 and 2 weeks postoperatively, and the serum estrogen was determined to verify the adequacy of replacement. The temporomandibular joints of the age-matched sham-operated control and ovariectomized groups were histomorphometrically evaluated at the same periods.

In OVX animals, the thickness of the articular soft tissue was increased by a concomitant increase of the transitional and cartilage zones in the anterior and posterior portions at 1 and 2 weeks postoperatively. However, the bone volume was decreased in the anterior and posterior portions at 2 weeks after the surgery and the condyle was flattened. Replacement with 17beta-estradiol restored most of the histomorphometric parameters. The thickness of articular soft tissue was increased in the anterior portion by an increase in the cartilage zone in the OVX + E2 group at 2 weeks postoperatively. Increase of bone volume was found at 2 weeks after hormone replacement with a corresponding increased osteoid surface and decreased quiescent surface in the central portion at 1 week postoperatively. A flattened condyle was still noted at 2 weeks postoperatively in the OVX + E2 animals despite the hormone replacement.

Estrogen in a physiologic concentration may play an important role in TMJ remodeling. Progesterone may be indispensable for remodeling, particularly contributing to morphogenesis.