The Effect of Ethinyl Estradiol/Norgestrel on Orthodontic Tooth Movement in Rats

Abstract

Abstract Introduction: The purpose of this study was to investigate the effect of ethinyl estradiol/norgestrel used in some oral contraceptive pills on orthodontic tooth movement in Wistar rats. Materials and Methods: Forty eight female three-month old Wistar rats with an average weight of 250 gr were selected and randomly divided into two experimental and control groups. One week prior to appliance insertion and during the appliance therapy period, 100 mcg/kg/day of ethinyl estradiol and 1mg/kg/days of norgestrel was administered to the experimental group by gavage; meanwhile the control group received an equivalent volume of Sodium Chloride 0.9 % (Saline). Maxillary central incisors were tipped distally by insertion of springs exerting 30g force. Two, seven and fourteen days after spring insertion animals were sacrificed. Then the mesioincisal distance between maxillary incisors were measured. Subsequently, histological sections were prepared to count osteoclasts under a light microscope. The data on the extent of orthodontic tooth movement, and the number of osteoclasts were analyzed by independent sample t-test. Results: The results indicated that 14 days after force application the orthodontic tooth movement was significantly lower in the experimental group (p<0.05). The number of osteoclasts were significantly lower in the experimental group 2, 7 and 14 days after spring insertion (p<0.05). Conclusion: Ethinyl estradiol/norgestrel can significantly decrease the amount of tooth movement in the linear phase. Also the number of osteoclasts is significantly decreased after drug administration in rats. Keywords: orthodontic tooth movement, ethinyl estradiol, norgestrel, osteoclast, oral contraceptive pill.,