Introduction & Objective: Maxillary canines are esthetically and functionally important, but patients with impacted maxillary canines are perceived to be more difficult and time-consuming to treat than the average orthodontic patient. The aim of this study was to define orthodontic Treatment Difficulty Index (TDI) of impacted maxillary canine with CBCT according to experts' opinions.

Materials & Methods: In this cross sectional study, nine variables in CBCT of thirty six consecutive patients with 50 impacted maxillary canines were measured using Dolphin 3D. The related 3D and 2D pictures and the measured data were uploaded on a website. Ten orthodontists were asked to judge the difficulty of bringing the impacted canine to occlusal plane from 1 to 10 (1 = easy, 10 = extremely difficult). Then, they were also asked to evaluate the effect of each variable on treatment from 1 to 5 (1= very low, 5= very high). Random effect linear regression was used in exploration stage and then simple linear regression was used for the application of the model.

Results: The patients mean age was 19.08 ± 5.8 years. Mean clinical experience of examiners was 22.7 ± 12.02 years. Three variables were deleted at exploration stage and two other in model application stage. Vertical distance to the occlusal plane (P=0.000), overlap in frontal view (P=0.000), angulations of the canine to the occlusal plan (P=0.029), dilacerations (P=0.000), and rotation (P=0.029) had a significant relationship with TDI.

Conclusion: Treatment difficulty of impacted maxillary canines could be predicted quantitatively by measuring variables in CBCT.