Abstract: Objective: To study the effect of orthodontic tooth movement on the level of estrogen in serum and local periodontal tissues in rats. Methods: One hundred and five female wistar rats were selected for the orthodontic tooth movement model and randomly divided into A (sham group), B (afterburner experiment group) and C (control group) group. Each group was also divided into four subgroups of proestrus, estrus, metestrus, and diestrus. Rat serum and local dental periodontal tissue estrogen levels were measured by radioimmunoassay and immunohistochemical methods, respectively. Results: Compared with the rats in proestrus and estrus periods, estrogen levels in serum and local periodontal tissue of rats in the late diestrus showed differences with statistical significance (P<0.05). In addition, from proestrus to estrus, metestrus, and then diestrus period, orthodontic tooth movement led to remarkable increase of estrogen levels in serum and local dental periodontal tissue (P<0.05). Conclusion: The increase of estrogen levels caused by orthodontic tooth movement can be attributed to the systemic stress response. The increased estrogen levels in local periodontal tissue resulted from periodontal reconstruction by local stress.

Key words: Estrogen, Orthodontic tooth movements, Estrous cycle