Abstract: Objective To evaluate root resorption of incisors from adult patients with Class Ⅱ division 2 malocclusion treated with three different orthodontic appliances. Methods Thirty patients were selected, including 10 cases treated with conventional MBT appliances, 10 cases with self-ligating appliances and 10 patients with clear aligners. In total, 240 incisors were researched. Cone beam computed tomography (CBCT) data were collected and imported into Dolphin Imaging software, Mimics and 3-Matics software to measure and analyze root variables of incisors pre- and post-treatment. Results The average tooth length(L) showed significant decrease after treatment for all maxillary and mandibular incisors in conventional MBT appliance group, self-ligating appliance group and central incisors, maxillary lateral incisors in clear aligner group. No significant decrease in mandibular lateral teeth average length were observed in clear aligner group. No statistically significant difference in tooth length of maxillary or mandibular central incisors was observed among three groups. In contrast, the reduction of maxillary and mandibular lateral incisors length in the clear aligner group was significantly lower(P＜0.05). The least average length reduction was found in clear aligner group (-0.37±0.11)mm, which was significantly lower than conventional MBT appliancegroup, (-1.32±0.47)mm and self-ligating group, (-1.05±0.38)mm.In addition, the three groups showed a higher prevalence of palatal and proximal resorption than labial and distal resorption. Conclusion Using clear aligners for treatment of Class Ⅱ division 2 malocclusions can effectively reduce severity of incisor root resorption.

Key words: Class Ⅱ division 2, orthodontic appliance, root resorption, incisor