Effect of orthodontic treatment with preadjusted edgewise appliances on the buccolingual inclination of mandibular canines: A CBCT study

Objectives: To assess the effects of treatment with preadjusted edgewise appliances on the buccolingual inclination of mandibular canines and the intercanine distance. Setting and Sample Population: The Division of Orthodontics at the University of Minnesota. Thirty patients whose treatment included extraction of mandibular first premolars and 30 patients whose treatment did not include extractions. Material and Methods: The buccolingual inclination of mandibular canines and their linear distance were measured on cone beam computed tomograms before and after treatment in both patient groups. Differences between extraction and non-extraction groups and between pre- and post-treatment measurements were tested for statistical significance, and the correlation between the buccolingual inclination and the intercanine distance was computed. Results: Post-treatment, the buccolingual inclination of mandibular canines was significantly greater in the non-extraction group than in the extraction group. In both groups, the canines became more lingually inclined with treatment (non-extraction group: -2.1°; extraction group: -4.1°). The intercanine distance increased significantly in the extraction group (+1.2 mm) but not in the non-extraction group (-0.5 mm). While there was a significant positive correlation between the buccolingual inclination and the mandibular intercanine distance in both groups before treatment, after treatment this correlation was significant only in the non-extraction group. Conclusion: Orthodontic treatment with preadjusted edgewise appliances results in more lingually inclined mandibular canines together with an increased intercanine distance, especially in patients whose treatment involves the extraction of mandibular first premolars.