A clinical review of external apical root resorption and self-repair of maxillary incisors after orthodontic treatment

The purpose of this study was to investigate the degree of root resorption after orthodontic treatment and self-repair of the root following two years of retention by measuring the root length of the maxillary incisors before, immediately after and two years after orthodontic treatment. Sixty patients with Angle Class II division 1 malocclusion ranging in age from 12 to 22 who were treated with bilateral maxillary first premolar extraction and a straight wire appliance were selected for the study. Parallel periapical radiographs were obtained, and the length of the maxillary incisor roots was measured before treatment (T1), immediately after treatment (T2) and two years after treatment (T3). A Wilcoxon signed-rank test and a chi-square test were used in the statistical analysis. In the present study, 97% of the incisors exhibited different degrees of external apical root resorption (EARR) after orthodontic treatment. The amount of EARR for the central incisors (1.1 mm) was significantly less than that for the lateral incisors (1.3 mm) (P=0.022<0.05). Significant differences were observed between the degree of EARR immediately after treatment and two years after treatment for both the central and lateral incisor groups (P<0.001). In conclusion, the resorption of the lateral incisors was much greater than that of the central incisors. Self-repair with cementum materialization occurred only in roots with mild or moderate resorption, and only a small portion of teeth with mild EARR could be fully regenerated or remodeled. Additional resorption occurred in roots with severe resorption, and no regeneration or self-repair was observed in these teeth.