Comparison of Root Resorption in Modified Corticotomy-Assisted and Conventional Canine Retraction

External apical root resorption is a known complication of orthodontic treatment and may be influenced by the magnitude and duration of orthodontic force. Methods that accelerate tooth movement may reduce overall treatment time and potentially influence the extent of root resorption. Corticotomy-assisted orthodontics is based on the regional acceleratory phenomenon, which enhances bone remodeling and facilitates tooth movement. Modified corticotomy techniques involve limited surgical injury to the cortical bone to stimulate accelerated movement while minimizing postoperative morbidity. Frictionless mechanics using T-loops allow controlled canine retraction with reduced frictional resistance between the bracket and archwire. This single-center randomized controlled clinical trial will enroll 60 patients aged 12 to 30 years who require bilateral extraction of maxillary first premolars as part of orthodontic treatment. Participants will be randomly allocated in a 1:1 ratio to: Group A: Modified corticotomy-assisted canine retraction with frictionless T-loop mechanics Group B: Conventional frictionless T-loop canine retraction All participants will be treated using 0.022 × 0.028-inch preadjusted edgewise appliances. Standardized T-loop activation delivering controlled force will be performed at three-week intervals until canine retraction is completed. External apical root resorption will be assessed by measuring linear changes in root length from the canine cusp tip to the root apex on calibrated pre- and post-retraction panoramic radiographs using digital measurement software. The primary outcome measure will be the mean change in root length between baseline and post-retraction assessments. Statistical analysis will compare the magnitude of root resorption between the two groups.