A Study Of Root Resorption Of Canine After Distal Movement

Objective: The purpose of this study was to determine the changes in the crown/root ratio of canines by comparing pretreatment and post-treatment panoramic radiographs. The influence of distal movement of canines on root resorption was analyzed. It also provides a reference for different orthodontic treatment options. and the method to prevent the root resorption.Methods: The sample consisted of 30 patients, aged 12 -14 years, treated with MBT straight wire appliance in The Affiliated Hospital of Stomatology of Chongqing Medical University between 2006 and 2010. 114 canines were selected for the study. Determination of the changes in the crown to root ratio of canine for each patient was established by comparing the panoramic radiographs that had been taken before and after treatment. The changes were compared in the 3 groups: experimental group 1, first premolars were extracted in pre-treatment;experimental group 2, second premolars were extracted in pre-treatment;control group, no extraction in pre-treatment. The changes were compared between maxilla and mandible of every group. Results:(1)The crown/ root ratio of canine in the experimental group 1 increased 0.026±0.113, but this was not significant (p=0.196).(2) The crown/ root ratio of canine in experimental group 2 decreased 0.011±0.091, but the change was not statistically significant (p=0.703).(3) The crown/ root ratio of canine in the control group decreased 0.046±0.091 and this change was statistically significant (p=0.002).(4) Statistically significant differences were obtained when experimental group 1 and control group were compared (p=0.005).(5)There was no obvious difference between experimental group 2 and control group (p=0.343).(6)There was no significant difference in amount of root resorption between upper and lower canines in every group.Conclusion:(1) Distal movement will lead to the resorption of canine root.(2)There is no difference in amount of root resorption of canines of the upper and lower arches under the same condition.