[Effects of EMD on relapse and root repair after orthodontic tooth movement in rats].

PURPOSE: To study the effect of enamel matrix derivative(EMD) on root repair and tooth movement relapse after orthodontic tooth movement in rats. METHODS: Twenty 10-weeks old male rats were divided into experimental and control group randomly (n=10). 100 g force was exerted to the left maxillary first molars for 14 days and then removed. EMD was injected in rats in the experimental group since appliance was removed. The control group received no injection. Micro-CT was taken to analyze the changes of root resorption volume and distance of tooth movement. The differences were analyzed by SPSS19.0 software package. RESULTS: Fourteen days after device removal, the repair volume of root resorption lacunae in the experimental group and the control group were (0.0295+/-0.0052)x10(7) mum(3)，(0.0189+/-0.0086)x10(7) mum(3), respectively. The relapse distance and relapse percentage after tooth movement were (0.089+/-0.005) mm, (64.76+/-3.63)%, (0.127+/-0.010) mm and (92.28+/-1.90)%, respectively. Statistical analysis showed the repair volume of root resorption lacunae, the relapse distance and relapse percentage were statistically significant 14 days after device removal (P<0.05). CONCLUSIONS: EMD can enhance the effect of root repair and decrease early relapse after orthodontic tooth movement in a certain extent.