Influences of ovariectomy on experimental tooth movement in the rat.

Estrogen withdrawal, which is important in the pathogenesis of post-menopausal osteoporosis, accelerates bone metabolism with a negative calcium balance. Therefore, it is hypothesized that estrogen deficiency could affect the rate of experimental tooth movement and alveolar bone remodeling. Six-week-old rats received a bilateral ovariectomy (OVX) or sham operation. Fourteen days later, rats were subjected to lateral tooth movement in the upper molar with nickel-titanium wire of 10 g of force. OVX significantly increased the rate of experimental tooth movement from 12 days after experimental tooth movement (p < 0.001). Eighteen days after the start of tooth movement, bone histomorphometry demonstrated that OVX significantly elevated the osteoblast surface, osteoclast surface, and number of osteoclasts (p < 0.05) in the alveolar bone. These findings indicated that estrogen deficiency caused significantly rapid orthodontic tooth movement, and that the acceleration of tooth movement could be due to the further activation of alveolar bone turnover.