Abstract: PURPOSE: To compare apical root resorption of maxillary incisors between adolescents and adults after orthodontic treatment. METHODS: Patients receiving orthodontic treatment in Affiliated Hospital of Chifeng University from May 2014 to August 2016 were enrolled, and divided into two age groups: adolescent group (32) and adult group (36). The included subjects received orthodontic fixed appliance treatment with straight-wire technique combined with Hawley type retainer for one year. After treatment, all patients were followed up for one year. Then the apical root resorption of maxillary incisors was evaluated by cone-beam CT (CBCT) at 4 time points, including pre-treatment (T1), end of treatment (T2), 6 months after treatment (T3), and 12 months after treatment (T4). Data were processed by SPSS 20.0 software package. RESULTS: The external root volume of maxillary central incisor, lateral incisors, mandibular central incisors and mandibular lateral incisors of both sides at T2-T4 was significantly lower than that at T1(P<0.05). There was partial increase in root volume of both groups at T3 and T4, while no significant difference from that at T2 (P>0.05). △root volume _T3-T2 and △root volume _T4-T3 had no significant difference between the two groups (P>0.05). △root volume _T3-T2 in the adolescent group was significantly smaller than that in the adult group (P<0.05). Correlation analysis showed that the △root volume_T1-T2 was significantly positively correlated with age (P<0.05), meanwhile △root volume _T3-T2 and △root volume _T4-T3 were negatively correlated with age (P<0.05). CONCLUSIONS: Age is an important factor affecting the volume of root after orthodontic treatment. Adolescent patients with Class II division 1 malocclusion have a strong ability of self-healing after orthodontic treatment.

Key words: Adolescents, Adult, Malocclusion, Orthodontic treatment, Maxillary incisors, Root absorption