Comparison of External Apical Root Resorption in Modified Corticotomy-Assisted and Conventionally Retracted Maxillary Canines Using Frictionless T-Loop Mechanics: A Randomized Controlled Clinical Trial

Abstract

Objective: To compare external apical root resorption in maxillary canines retracted using modified corticotomy-assisted and conventional frictionless T-loop mechanics.

Methodology: A randomized controlled clinical trial NCT07458139- www.clinicaltrials.gov was conducted in the Department of Orthodontics at Islamabad Dental Hospital over a period of 1.5 from  July 2024 to Dec 2025, on 60 maxillary canines in 30 patients requiring extraction of maxillary first premolars. Canines were divided into two groups: Group A (modified corticotomy-assisted retraction using T-loop frictionless mechanics) and Group B (conventional frictionless retraction using T-loops). Root length and root apex width (mesial and distal) were measured on pre- and post-treatment orthopantomograms (OPGs). The amount of root resorption was calculated as the difference between pre- and post-treatment measurements. Paired sample t-tests were used for intragroup comparisons, and independent sample t-tests were used for intergroup comparisons. Normality was assessed using the Shapiro–Wilk test.

Results: Both Group A and B demonstrated statistically significant reductions in root length following canine retraction. The mean root resorption was significantly lower in the corticotomy group (0.33 ± 0.66 mm) compared with the conventional group (0.96 ± 0.82 mm). Mesial root width showed a statistically significant reduction in the corticotomy group, whereas distal root width changes were minimal and not statistically significant in either group. No variability was observed in mesial root width reduction in the conventional group.

Conclusions: Modified corticotomy-assisted canine retraction results showed significantly less external apical root resorption compared with conventional frictionless mechanics.