Evaluation of the changes of root surface of the premolars that are in contact with miniscrew by micro computed tomography

Aim: The purpose of this prospective clinical study was to determine the three-dimensional resorption volumes that occured in the root surface of upper first premolars which were moved to directly contact the miniscrews, and to learn about the repair process after different retention periods (4, 8, 12 weeks). Materials and Method: Forty two patients who were treated with routine orthodontic fixed appliance and whose orthodontic treatment plan required bilateral first premolar tooth extraction were included in this study. Upper first premolars were inserted 0.017''x.025'' TMA cantilever springs which applied 150 g force and 1,5 mm diameter, 8 mm long miniscrews were placed in the distal interradicular region. Right first premolars of all patients were extracted after 4 weeks of mini screw insertion. The first 4 weeks of the application was same for left first premolars and for investigating repair process tooth was extracted by the 4th, 8th and 12th weeks of retention periods. Repair process was monitored for searching the effect of factor and force application on retention period after mini screw (factor) removal in the first three groups and after spring (force) removal in the other three groups. At the end of the process, resorption craters of premolar root surface were examined with SkyScan 1172 Micro CT and CTAn 1.15.4.0 programme. Kruskal-Wallis one-way analysis of variance and Mann-Whitney U test were conducted as the post hoc test after Bonferroni correction was used for statistical assessment. Results: With respect to resorption crater volume evaluation, retention period of 4 weeks more volume were measured in the experimental group than in the control group. In the group of force elimination, repair process have increased after 8 weeks. In the groups of factor elimination, the results of 4 weeks retention were more than 8 and 12 weeks. Conclusions: After contact damage of root with miniscrew, during the repair of resorption craters, force elimination is more effective for more effective realization of repair mechanisms than factor elimination. For complete repair of resorption craters, 12 weeks of retention period is not enough.