Effects of estrogen deficiency on tooth movement after force application: an experimental study in ovariectomized rats

Objective. The aim of this study was to investigate the effects of estrogen deficiency on tooth movement in ovariectomized rats. Material and methods. Forty-two adult female Sprague-Dawley rats were assigned at random to one of the following groups: test group (n=20), ovariectomized rats (or estrogen-deficient rats); control group (n=22), non-ovariectomized rats. Two months after ovariectomy, expansion springs exerting 10 g of force were inserted between the upper central incisors in both groups. The amount of movement was measured daily until tooth movement began and then at intervals of 3 days. The rats were sacrificed 18 days after applying the expansion spring and histomorphometric analysis was performed along the left upper central incisor root towards the apex of the alveolar bone. Results. The amount and speed of movement was observed to be greater in ovariectomized rats. On histomorphometric analysis, osteoblast and osteocyte counts on the pressure side were higher in the non-ovariectomized group than in the ovariectomized group (p < 0.001). In contrast, the osteoclast count was significantly higher (p < 0.01) in the ovariectomized group than in the non-ovariectomized group. The osteoblast and osteocyte counts were significantly higher (p < 0.001) on tension side in the non-ovariectomized group than in the ovariectomized group. Conclusion. Estrogen deficiency increased orthodontic tooth movements but counts of osteoblasts, which are responsible for new bone formation, were lower in regions of tension and of pressure.