Abstract
OBJECTIVE: To evaluate the effect of gradually increasing orthodontic force magnitude compared with a constant force magnitude on the rate of tooth movement during maxillary canine retraction. METHODS: This split-mouth randomized controlled clinical trial included 15 patients (30 sides). Each patient received both interventions. On the intervention side, canine retraction was performed using nickel–titanium closed-coil springs delivering progressively increased forces of 50 g, 100 g, and 150 g over three consecutive monthly intervals. On the control side, a constant force of 150 g was applied throughout the study period. Maxillary arch impressions were obtained at baseline (T0) and at 4-week intervals for three months (T1, T2, and T3). Digital model analysis was used to assess the rate and total amount of canine movement. RESULTS: No statistically significant difference was observed between the two sides in the monthly rate of canine retraction at any time point (P > 0.05). The total distance of canine movement was 2.58 ± 0.70 mm in the control side and 2.24 ± 0.82 mm in the intervention side, with no significant intergroup difference (mean difference = 0.34 ± 1.08 mm, P > 0.05). CONCLUSION: Gradually increasing orthodontic force magnitude did not enhance the rate of maxillary canine retraction compared with a conventional constant force protocol. CLINICAL RELEVANCE: Progressive force escalation during canine retraction does not provide a clinical advantage over constant force application, supporting the use of simpler, continuous force mechanics in routine orthodontic practice. TRIAL REGISTRATION: The trial was registered in ClinicalTrials.gov Identifier: NCT05643443. https://clinicaltrials.gov/study/NCT05643443. Registered December 18, 2022. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12903-026-08243-4.