Force-induced increased osteogenesis enables accelerated orthodontic tooth movement in ovariectomized rats

As the number of elderly orthodontic patients increases, the impact of postmenopausal osteoporosis on orthodontic tooth movement (OTM) has attracted a great deal of attention because OTM relies on alveolar bone remodeling. The question of whether OTM causes subsequent alveolar bone loss and is harmful to alveolar bone health under osteoporotic conditions remains to be answered. The present study aimed to clarify the influences of OTM on alveolar bone in osteoporotic rats. OTM was accelerated in ovariectomized (OVX) rats as a result of increased bone resorption in the pressure area. At the same time, anabolic bone formation was promoted in the tension area during OTM in OVX rats. Micro-CT analysis of alveolar bone revealed a decrease in BMD, BV/TV and Tb.Th. in the OTM group compared with that in non-OTM rats on day 21 of OTM, suggesting that OTM caused alveolar bone loss in OVX rats during OTM. However, the OTM-induced bone loss could be recovered 3 months after OTM in OVX rats. Thus, our findings suggest that increased osteogenesis may compensate for the increased bone resorption during and after OTM and enable effective accelerated OTM in OVX rats.