[Failure in the orthodontic treatment of impacted maxillary canines]

Maxillary canine impaction occurs in 1-3% of most Western populations and its orthodontic treatment is often difficult. Failure to resolve the impaction is not uncommon and may lead to malpractice lawsuits. The information in the literature about the reasons for non-resolution of this condition is sparse and unsubstantiated. This encourages the dispensing of inappropriate treatment that may result in severe tooth, soft and hard tissue damage as well as a prolonged treatment period. This review describes the epidemiology, pathogenesis and the wide range of reasons that may lead to failure to resolve the canine impaction. It shows that a lack of appreciation of anchorage demands and inaccurate positional diagnosis of the 3-D location and orientation of impacted teeth are the major reasons for failure. In addition, the review shows that invasive cervical root resorption (ICRR) is a frequently undiagnosed or unrecognized cause of failure of orthodontic resolution of impacted canines, and should be distinguished from replacement resorption (ankylosis). Corrective measures which may lead to successful treatment are further recommended. Special emphasis is placed on the crucial role of cone beam computerized tomography in the accurate radiographic diagnosis and early detection of pathology of impacted tooth and damage to adjacent anchor teeth. The importance of teamwork in achieving the best treatment outcome is stressed.