Predicting and preventing root resorption: Part II. Treatment factors

The main objective of this study was to determine which treatment factors a re most clearly identified with external apical root resorption that is det ectable on periapical radiographs at the end of orthodontic treatment. The records of 868 patients who completed fixed, edgewise treatment from experi enced clinicians in private practice were examined. The horizontal and vert ical displacement of the root apex of the maxillary central incisor was mea sured on cephalometric radiographs. Patients who underwent first premolar e xtraction therapy had more resorption than those patients who had no extrac tions or had only maxillary first premolars removed. Duration of treatment and the horizontal (but not vertical) displacement of the incisor apices we re significantly associated with root resorption. No differences were found for slot size, archwire type, use of elastics, and types of expansion. How ever, there was considerable variation among the 6 offices that were survey ed; 1 office averaged nearly a full millimeter more of resorption per anter ior tooth than the office with the least amount of root resorption. We conc lude that the clinician should exercise caution with those patients in whom extraction therapy is planned for overjet correction that requires above a verage treatment time. Finally, each clinician should be aware that the roo t resorption seen in one practice may be different from the root resorption found in another practice.