Effects of tooth root contact on the stability of orthodontic anchor screws in the maxilla: Comparison between self-drilling and self-tapping methods

•The self-drilling screws tended to contact distal tooth roots in the right maxilla.•The self-drilling failure rate was higher in the root contact group than in the no-contact group.•Success rates were not significantly different between self-drilling and self-tapping methods.•Avoidance of tooth root contact may improve the success rate more in the self-drilling method.

IntroductionWe evaluated the effects of screw placement angle on the frequency of root contact and the effects of root contact on screw stability, comparing self-drilling and self-tapping methods.MethodsIn total, 80 patients with 142 screws (diameter, 1.6 mm; length, 8.0 mm) were included. Cone-beam computed tomography images were taken. Cortical bone thickness, interroot distance, shortest distance between the screw and adjacent tooth root, and screw placement angle were measured.ResultsThe success rates of the screws were 91.5% for the self-drilling method and 94.4% for the self-tapping method (P >0.05). The self-drilling screws tended to contact the distal tooth roots in the right maxilla. In the self-drilling method, the failure rate was significantly higher in the root contact group than in the no-contact group (P <0.05).ConclusionsThe success rate was not significantly different between the self-drilling and the self-tapping methods in the maxilla. Avoidance of tooth root contact may improve the success rate more in the self-drilling method than in the self-tapping method.