Eperimental study on the effects of ovariectomy and estrogen on the bone pattern of mandible in rats

Lee, Hyung Soon; Hong, Sung Gyu; Kim, Jong Ghee

Abstract

The purpose of this study was to evaluate the changes of cancellous and cortical bone and the effect of estrogen in ovariectomized rats. Fifty female rats, 250gm in body weight, were divided into three groups : ovariectomized group(OVE), ovariectomized and estrogen-injected group(OVE-EST), and sham operated and estrogen-injected group(EST), Bilateral ovariectomy was performed at the onset of the experiment. In OVE-EST group and EST group, estrogen was injected 50microgram/kg B.W. every other days from 3 weeks after surgery to sacrifice Each five rats were sacrificed after 5, 6, 7 weeks. One side of mandibular body was radiographed with a soft x-ray apparatus (Hitex Co., Ltd., Japan). Thereafter the obtained microradiographs were used for the morphometric analysis using a Image analyzer. The morphometric analysis was performed for parameters such as total bone area, cortex bone area and medullary one area. The other side of the mandibular bone was decalcified and embedded in paraffin as using a general method. The specimens were sectioned and stained with Mallory`s anilline blue and observed light microscopically. The results were as follows. 1. In all groups, the proportion of cortex to total bone area was not significantly different. 2. In ovarietomized(OVE) group, the proportion of marrow cavity to medullary bone area increased significantly from 5 to 7 weeks(p<0.05). In ovariectomized and estrogen-injected (OVE-EST) group, it decreased significantly at 7 weeks, and in estrogen-injected(EST) group, it decreased significantly from 6 week(p<0.05). 3. Microradiogram and histopathologic findings revealed that marrow cavity was enlarged and osteoclasts were observed around irregular bone surface in OVE group. In OVE-EST group, the size of marrow cavity at 7 weeks was similar to that of control group, as dense trabecular bone increased from 5 to 7 weeks, marrow cavity decreased.