Altered bone remodeling pattern of the residual ridge in ovariectomized rats

This study investigated the effect of estrogen deficiency on residual ridge remodeling after tooth extraction. Ovariectomy was performed on female Sprague-Dawley rats, and the plasma levels of estrogen and progesterone were monitored. The maxillary molars of the ovariectomized and control rats were extracted and the remodeling residual ridge tissues were harvested at 2, 4, and 8 weeks postextraction. The specimens were examined at the mesiodistal center point of the residual ridge by use of light and scanning electron microscopy. The surface of the residual ridge of the control animals showed a number of osteoclastic lacunae indicating bone resorption activity. In the ovariectomized animals, the surface of the residual alveolar bone was partially covered by a distinct calcified tissue. This tissue contained large cells and a mesh-like structure of thin calcified extracellular matrix consistent with the tissue characteristics of chondroid bone. The chondroid bone-like calcified tissue was found only in the ovariectomized animals throughout the experiment period. This study's data suggest that a systemic condition such as estrogen deficiency due to ovariectomy may alter the phenotypic expression of cells associated with the residual ridge and result in less osteoclastic activity and a different type of calcified tissue.