Abstract: Objective This study aims to identify the effects of corticotomy-assisted orthodontic premolar intrusion and evaluate the changes of root resorption and the alveolar bone. Methods Both sides of the mandible of eight male Beagle dogs were randomly assigned into experimental and control groups. The third (P3) and fourth (P4) premolars were intruded with both mini-screw implant anchorage (MIA) and corticotomy on the experimental side. By contrast, P3 and P4 were intruded with MIA alone on the control side. During pre-operation and after 2, 4, 8, and 12 weeks of orthodontic force applications, cone beam computed tomography was performed on every dog. The distance of tooth intrusion and root resorption of furcation, as well as the apex and height changes of the alveolar bone were measured and analyzed. Results The intrusion distance of premolars on the experimental side was greater than that on the control side (P<0.05). The root of furcation and apex on both sides occurred in root resorption, and the root resorption of the apex on the experimental side was lighter than that on the control side after 12 weeks of force application (P<0.05). The alveolar bone height decreased, and the height reduction distance on the experimental side was greater than that on the control side after 8 and 12 weeks of force application (P<0.05). Conclusion Corticotomy accelerates orthodontic molar intrusion and reduces root resorption.

Key words: mini-screw implant anchorage, corticotomy, intrusion movement, root resorption