Objective: To compare the space closure, root resorption and canine angulation during en-masse retraction of the labial segment after extraction of first premolars with or without interseptal bone reduction distal to the maxillary canines.
Design: A single-centre, parallel randomised control trial included 16 participants with a mean age of 21.5 years. Participants were allocated into treatment groups using blocked randomisation, and blinding was employed for outcome assessors and data analysts.
Interventions: The control group consisted of eight participants who underwent therapeutic extraction of maxillary first premolars, while the experimental group included eight participants who underwent interseptal bone reduction immediately after premolar extraction. En-masse retraction was performed using conventional friction mechanics with absolute anchorage in both groups.
Outcomes: Measurements of space closure were conducted over 3 consecutive months during retraction. The time taken for total space closure was recorded. Cone-beam computed tomography scans were taken before and 3 months after retraction to assess root resorption and canine angulation.
Results: The experimental group demonstrated a significant increase in the rate of en-masse retraction compared to the control group over 3 months (mean difference [MD] = 1.09 mm, 95% confidence interval [CI] = 0.78-1.40), with an overall space closure rate of MD 0.26 mm/month (95% CI = 0.17-0.34). However, these changes were of minimal clinical significance. The change in canine angulation (MD = 4.50°, 95% CI = -1.61-10.61) did not exhibit statistical significance. Substantial root resorption was observed in six maxillary anterior teeth, with no difference between the groups.
Conclusion: Interseptal bone reduction is a minimally invasive surgical technique, resulting in a notably accelerated rate of en-masse retraction in the experimental group over 3 months. However, despite the statistical significance, the clinical impact on overall space closure was minimal, with a difference of only 0.26 mm/month observed between the groups. Interseptal bone reduction did not affect the change in canine angulation and root resorption.
Keywords: canine angulation; cone-beam computed tomography; en-masse retraction; interseptal bone reduction; minor oral surgery; orthodontic interface; regional acceleratory phenomenon; root resorption.