Are there differences on tooth movement between different sectional canine retractors?

The aim of this study was to compare the effects of two retraction springs, demonstrating differences in reactivation and constancy of force, on tooth movement during canine distalization. Upper and lower canines of 16 patients (9 females, 7 males; mean age 14.6±1.7 years) with Angle Class I or II malocclusion were included in the study. Left upper and lower canines were distalized using Poul Gjessing (PG) retractors, whereas right canines of the same patients were distalized using Hybrid retractors. Angular and linear measurements were performed on lateral cephalometric radiographs and dental models taken prior to and at the end of canine distalization. Paired Samples t-test, Repeated Measures of Analysis of Variance and Greenhouse-Geisser tests were used for statistical analysis. The mean rates of canine distalization in PG retractors were 1.03 and 0.88 mm/months and 1.13 and 0.93 mm/months for Hybrid retractors for upper and lower canines, respectively. No significant differences were detected in the rate of canine distalization, sagittal and vertical movement of canines, and first molars between retractors or arches. Despite the differences in reactivation and constancy of the forces between PG and Hybrid retractors, both revealed similar canine distalization, distal tipping, rotation, and anchorage loss of molars. As a clinical point of view, Hybrid retractors could provide more benefits due to fewer activation requirements.