Patient characteristics and treatment variables associated with apical root resorption during orthodontic treatment.

Multivariate analysis of patient characteristics and clinical variables was carried out with the maximum single maxillary incisor apical root resorption for each patient as the dependent variable. Root lengths were measured in standardized intraoral radiographs from 485 consecutively treated patients, 11.5 to 25 years of age. The correlation matrix revealed a complex pattern of positive and negative associations between the six pretreatment and seven treatment variables. Variables found to contribute significantly to apical root resorption were overjet, history of trauma to maxillary incisors before initiation of treatment, time of treatment with rectangular arch wires, time of treatment with Class II elastics, lip/tongue dysfunction, and/or history of finger-sucking habits persisting beyond the age of 7 years, and impacted maxillary canines to be corrected orthodontically. Clinical application of an open activator was significantly correlated with overjet but negatively correlated with apical root resorption, with the use of rectangular arch wires and/or Class II elastics, and with total banding time.