Failure rates and associated risk factors of orthodontic-surgical treatment for impacted canines.

Objectives: To determine failure rates of orthodontic-surgical treatment for maxillary and mandibular impacted canines and identify patient- and treatment-related risk factors of failure, increased duration, and need for surgical reintervention. Materials and Methods: Panoramic radiographs and clinical records of patients who consecutively visited the Postgraduate Clinic of the Department of Orthodontics of the Aristotle University of Thessaloniki, Greece, were retrospectively retrieved and analyzed. Two statistical analyses were conducted, using canine and patient as units of analysis, respectively, to account for bilaterally impacted canines, resulting in multiple observations per individual. Linear and logistic regression models were employed. Results: A total of 84 patients with 106 impacted canines were included. An overall failure rate of 11.3% was reported. With canine as the analysis unit, age was the only significant risk factor for failure, while both age and exposure technique were linked to the need for reintervention. In the mixed-effects regression model, age remained the only significant risk factor for both failure and reintervention. Regarding increased duration, an association was detected with increased angulation, proximity to midline, and closed exposure. Conclusions: Increased age is a significant risk factor for treatment failure and surgical reintervention of impacted canines, while greater angulation, proximity to midline, and closed over open exposure may be associated with prolonged treatment.