Effects of 17β-Estradiol Deficiency and Mechanical Overload on Osseous Changes in the Rat Temporomandibular Joint.

Purpose: To deduce the contributing factors to idiopathic condylar resorption in young female patients, we hypothesized that 17β-estradiol (E2) deficiency would cause arthritic changes in the mandibular condyle under mechanical overloading in a rat model. We also hypothesized that osseous changes in the microstructure by the combination of E2 deficiency and mechanical overloading would be different depending on the region of the condyle.

Materials And Methods: The mandibular condyles of female Sprague-Dawley rats were mechanically overloaded (50g) 8 weeks after an ovariectomy (OVX). Changes in the condyles were analyzed with micro-computed tomography and histochemical and immunohistochemical staining.

Results: The size of the mandibular condyle decreased significantly with OVX or mechanical loading. The incidence of arthritic changes, including osteophyte formation, bone erosion, and flattening, was significantly different between the sham and OVX groups. The posterior parts of the condyles showed poor bone quality before OVX, and their condition significantly worsened with reduced bone mineral density and bone volume/tissue volume, as well as a sparse trabecular pattern.

Conclusions: E2 deficiency and mechanical overloading of the temporomandibular joint cause morphologic changes in the mandibular condyle and changes in the osseous microstructure, which are more apparent in areas of poor bone quality.