RESUMEN
BACKGROUND: Preliminary studies have found that the oral intake of contraceptives reduces the rate of orthodontic tooth movement. This study mainy explores the effects of oral contraceptives on periodontium remodeling during orthodontic tooth movement in a female rat model. OBJECTIVE: To investigate the effects of combined oral contraceptives (COCs) on the expression levels of progesterone receptor and osteoprotegerin, as well as the number of osteoclasts in the periodontium during orthodontic tooth movement. METHODS: Eighty 3-month-old female Sprague-Dawley rats were randomly divided into two groups (n=40 per group), and COCs (marvelon, experimental group) or normal saline (control group) was then given by gavage. At 7 days after administration, the right maxillary first molars were moved mesially under a force of 50 g delivered by nickel-titanium coil springs, and 10 rats were killed on day 7, 14, 21 and 28 after loading, respectively. The expression levels of progesterone receptor and osteoprotegerin in the periodontium were detected by immunohistochemistry, and the number of activated osteoclasts was measured by tartrate-resistant acid phosphatase staining. RESULTS AND CONCLUSION: At 28 days after force loading, the expression level of progesterone receptor in the periodontium in the experimental group (0.307±0.03) was significantly higher than that in the control group (0.194±0.11), (P < 0.01). The number of osteoclasts in the maxillary first molars in the experimental group was significantly less than that in the control group at 7, 14, 21 and 28 days after force loading (P < 0.05). The average absorbance value of osteoprotegerin in the experimental group was significantly higher than that in the control group (P < 0.01). These results show that COCs are able to promote osteogenesis and slow bone absorption during periodontal reconstruction, indicating that the course of orthodontic treatment for female patients with a history of COCs intake may be extended.