title: Effect of estrogen replacement on temporomandibular joint remodeling in ovariectomized rats.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Estrogen in a physiologic concentration may play an important role in TMJ remodeling. Progesterone may be indispensable for remodeling, particularly contributing to morphogenesis.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Gifu University School of Medicine, Japan. yasuoka@cc.gifu-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Yasuoka
authors.forename: M
authors.initials: M
authors.lastname: Nakashima
authors.forename: T
authors.initials: T
authors.lastname: Okuda
authors.forename: N
authors.initials: N
authors.lastname: Tatematsu
mesh_terms: D000818:Animals; D016723:Bone Remodeling / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D015914:Estrogen Replacement Therapy; D005260:Female; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013704:Temporomandibular Joint / Q000033:anatomy & histology / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors
chemical_list: D004958:Estradiol