Changes in maxillary incisor inclination and position after traction of unilateral vs bilateral maxillary impacted canines in nonextraction treatment: A cone-beam computed tomography study

Introduction: The aim of this study was to compare the inclination and position changes of maxillary incisors after traction of unilateral vs bilateral maxillary impacted canines in nonextraction orthodontic treatment. Methods: This longitudinal and retrospective study evaluated 24 patients with impacted maxillary canines; 12 with unilateral impaction and 12 with bilateral impaction. All subjects had Angle Class I malocclusion and were orthodontically treated with a standardized traction protocol that did not include premolar extractions. Cone-beam computed tomographies were obtained before and after canine traction and the inclination and position of both maxillary central incisors were measured. Furthermore, dental arch, skeletal, and canine impaction characteristics were evaluated. Paired and independent t tests were used for intra and inter group comparisons, respectively. Multiple linear regressions were also used. Results: After canine traction, a significant incisor labial inclination was observed in the bilateral group (10.41° right side, P = 0.008 and 12.79° left side, P = 0.001), while in the unilateral group, this was observed only on the nonaffected side (6.67°, P = 0.008). Furthermore, a significant protrusion of incisors was observed in the bilateral group (2.66 mm right side, P = 0.006, and 3.15 mm left side, P = 0.001) and in the nonaffected side of the unilateral group (1.74 mm, P = 0.022). Intergroup comparisons showed greater values of incisor labial inclination for the bilateral group when compared with the unilateral group, independently of the sides. Conclusions: Traction of maxillary impacted canines, in nonextraction treatment, produces greater labial inclination of maxillary incisors in bilateral cases and similar protrusion in both unilateral and bilateral cases. Unilateral impaction cases showed significant incisor inclination and protrusion in the nonaffected side. These treatment effects should be considered by clinicians.