Impact of orthodontic forced eruption timing on root development of impacted maxillary canines: a linear and volumetric analysis using cone-beam computed tomography images.

Objectives: To evaluate root development after forced eruption of impacted maxillary canines before or after complete root development of the contralateral canine.

Materials and methods: A total of 50 patients (21 male, 29 female; mean age: 12.4 years) with unilateral impaction of maxillary canines were classified to "Immature group" with incomplete root development of the contralateral canine or "Mature group" with complete root development of the contralateral canine. Volume, total length, crown length, root length, and root/crown ratio (R/C) of the impacted canine and the contralateral canine were measured in the posttreatment cone-beam computed tomography images.

Results: In the immature group, total length and root length of impacted canines were 0.68 mm and 0.51 mm shorter than contralateral canines, respectively (P < .05). In the mature group, volume, total length, root length, and R/C of impacted canines were 37.90 mm3, 2.43 mm, 2.53 mm, and 0.26 smaller, respectively, than contralateral canines (P < .001). Crown length also showed a statistically significant difference between impacted canines and contralateral canines (P < .05). When differences between impacted canines and contralateral canines were compared between the immature and mature groups, all variables showed statistically significant differences, with the mean difference in total length and root length being 1.75 mm and 2.02 mm larger, respectively, in the mature group, (P < .001).

Conclusions: Regardless of treatment timing, total length and root length of impacted canines were shorter than those of contralateral canines. Forced eruption of the impacted canine undertaken before root development of the contralateral canine showed better root development in both linear and volumetric measurements.