External Apical Root Resorption in Maxillary Incisors of Orthodontic Patients

External apical root resorption is an irreversible process and unpredictable. Objectives: to evaluate the incidence and degree in external apical root resorption in maxillary incisors after orthodontic treatment and to evaluate associated particular factors related to external apical root resorption., Methods: The records and maxillary incisor periapical radiographs of 181 patients, treated with full fixed edgewise appliance were investigated. Crown and root length were measured by using a digital veneer caliper and compared between the pre- and post-treatment periapical radiographs. Crown length was measured from center of incisal edge to median CEJ point. Root length was measured from median CEJ point to root apex. A correction factor for enlargement difference was used to calculate external apical root resorption. Results: The periapical radiographs of 564 teeth showed that average external apical root resorption was 1.39 ±1.27 and 1.69 ±1.14 mm or 8.24 ± 7.22 and 10.16 ± 6.78 percents for maxillary central and lateral incisors, respectively. Dilacerated or pointed roots, upper premolar extraction cases and treatment duration were highly significant factors of external apical root resorption (P < 0.001). Allergic condition was significant factor at P < 0.01. Age at the start of treatment, overjet and history of facial trauma were also significant factors of root resorption (P < 0.05). There was no statistically significant difference in root resorption among sex, overbite, tongue thrusting habit, types of malocclusion and types of bracket., Conclusion: External apical root resorption can occur after orthodontic treatment. Patients with high risks of root resorption should be careful evaluated.