Effect of Daidzein on Inhibiting the Relapse of Bone Resorption after Orthodontic Treatment in A Rat Model of Middle-aged Female Patients

In recent years, an increasing number of middle-aged female patients have requested orthodontic treatment. Although retainers are used after orthodontic treatment, dentition relapses can occur. Daidzein（DZ）is used to treat osteoporosis as it can inhibit bone resorption and promote bone formation. This study aimed to investigate the effect of DZ on dentition relapse after orthodontic treatment in middle-aged females, focusing on the inhibitory effect it has on bone resorption. To investigate the effect of DZ on bone resorption, the experiment was initiated in female Wistar rats（n = 36）that were ovariectomized at 60 and 88 days of age. Rats were randomly divided into two groups: the DZ group, in which DZ was administered during the retention period, and the Control group, in which teeth were moved over a 14 day period and retention was performed for 14 days. After retention, dentition relapse was observed for 14 days. Immunohistochemical staining was performed using TRAP, RANKL, and OPG involved in bone resorption. Both the DZ and Control groups showed a significant increase in RANKL-positive cells and osteoclasts on day 14. On day 28, OPG-positive cells increased, and RANKL-positive cells and osteoclasts decreased in the DZ group compared with those in the Control group. This suggests that DZ administration may inhibit bone resorption after dynamic orthodontic treatment in middle-aged females, thereby reducing the risk of dentition relapse.