Effect of estrogen replacement on temporomandibular joint remodeling in ovariectomized rats

Purpose: The investigation was performed to elucidate,the effect of estroge n on the temporomandibular joint (TMJ) and to evaluate the therapeutic effe ct of 17 beta-estradiol replacement in growing rats. Materials and Methods: Thirty 4-week-old female albino Wister rats were div ided into 3 groups. Ten rats were ovariectomized followed by intramuscular administration of 17 beta-estradiol for hormone replacement (OVX + E-2), 10 were sham operated (CTL), and 10 were ovariectomized without hormone repla cement (OVX). Five rats from each group were killed at 1 and 2 weeks postop eratively, 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 t he same periods. Results: In OVX animals, the thickness of the articular soft tissue was inc reased by a concomitant increase of the transitional and cartilage zones in the anterior and posterior portions at 1 and 2 weeks postoperatively. Howe ver, the bone volume was decreased in the anterior and posterior portions a t 2 weeks after the surgery and the condyle was flattened. Replacement with 17 beta-estradiol restored most of the histomorphometric parameters. The t hickness of articular soft tissue was increased in the anterior portion by an increase in the cartilage zone in the OVX + E-2 group at 2 weeks postope ratively. increase of bone volume was found at 2 weeks after hormone replac ement with a corresponding increased osteoid surface and decreased quiescen t surface in the central portion at 1 week postoperatively. A flattened con dyle was still noted at 2 weeks postoperatively in-the OVX + E-2 animals de spite the hormone replacement. Conclusions: Estrogen in a physiologic concentration may play an important role in TMJ remodeling. Progesterone may be indispensable for remodeling, p articularly contributing to morphogenesis.