Extent and prognosis of apical root resorption due to orthodontic treatment

Root resorption is the most common side effect of orthodontic treatment and usually occurs within the first 6 months of treatment. Circumferential apical root resorption represents full resorption of the apical hard tissue components and evident root shortening. Although rarely serious it is a devastating event when recognized radiographically. The purpose of this article is to provide the dental practitioner with the results of studies on the extent of apical root resorption detected with clinical radiographs in patients treated with fixed appliances during or after orthodontic treatment and to provide the answers to the following questions: which teeth are most affected by apical root resorption, what happens to the resorbed tooth and what does the prognosis look like? The results could provide the best available evidence for clinical decisions to minimize the risk and severity of apical root resorption.

Study selection criteria included retrospective studies on human subjects for orthodontics with fixed appliances and apical root resorption recorded on X-rays (e.g. periapical films, panoramic films and lateral cephalometric studies) during or after orthodontic treatment. In the current literature the large variation in the methodological approaches and reporting results of data did not permit quantitative statistical comparisons and meta-analyses so that a systematic review was performed.

Evidence suggests that orthodontic treatment causes increased incidence and severity of apical root resorption. Apical root resorption occurs mainly in anterior teeth and affects maxillary teeth more severely than mandibular teeth: primarily affected are lateral incisors followed by central incisors, canines, then mandibular canines, central incisors and lateral incisors. Mean values ranged from 0.5 to 3 mm or 3–15 % of root shortening during orthodontic treatment. The average size of molar and premolar resorption was less than 1 mm. There were no reports of tooth loss due to apical root resorption in the literature. Regarding vitality and color, root resorbed teeth remain unchanged.

Follow-up of patients with severe orthodontically induced root resorption requires radiographic monitoring at 3- to 6-month intervals during treatment. In patients with enhanced risk of resorption a 3-month radiographic follow-up is recommended. Special attention should be paid to anterior teeth considering that these are the most affected by apical root resorption. It is recommended that the best practice is the use of light force especially for intrusive moments and root torque.The current clinical recommendations are to be very careful when moving anterior teeth over a long distance and a long time, especially if the teeth have abnormal root morphology.

Prevention and early diagnosis of root resorption require future research on genetic and molecular biological mechanisms. Considerable variation and unpredictability of resorption pertain to orthodontic information, patient education before consent is granted.