[Effects of pregnancy on orthodontic tooth movements: effects of progesterone on orthodontic tooth movements in pregnant rats].

This study evaluated the periodontal responses and progesterone changes to orthodontic tooth movements in pregnant rats. Adult female Sprague-Dawley rats were separated into two groups: non-pregnant and pregnant. All rats were treated with fixed orthodontic appliances that moved the upper incisors in a distal direction during 10 days. At the end of the experiment, the periodontal tissues were examined histologically and immunohistochemically (ABC method). The results showed that in the histological examination of the tension sides of the upper incisors, the bone formation was more obvious in the pregnant group than that in the non-pregnant group. In the immunohistochemical staining, the osteoblasts were positive-stained cells and they exhibited deeper stain and higher percentage in the pregnant group. In a conclusion, the progesterone influences the periodontal reconstruction on orthodontic tooth movements in pregnant rats and may be helpful in alveolar bone formation, which suggests that orthodontic treatments in pregnant patients may not be so harmful as people thought before.