Effect of archwire size on the rate of canine retraction in adult women: A randomized clinical trial

Abstract

Introduction: The purpose of the present study was to investigate the rate of upper canine retraction utilizing three different sizes of archwires. Materials and methods: In all, 36 upper canines of 18 adult females (21 ± 5 years) were allocated into three-arm parallel groups where canine retraction was attempted. In the first group (G16) 0.016–0.022-inch stainless steel wires (SS) were applied, in the second group (G17) 0.017–0.025-inch SS, and in the third group (G19) 0.019–0.025-inch SS, respectively. The eligibility criteria included patients with maxillary dentoalveolar protrusion that required extraction of first premolars as part of their treatment, mild crowding (< 5 mm), and full permanent dentition. Patients with active periodontal disease, systemic disease, medications or habits that would affect tooth movement were excluded. Randomization was performed using computer-generated numbers and the participants were allocated to each group according to their number in the randomization sheet. Canines were retracted using a closed nickel–titanium coil spring applying 1.5 N retraction force. The primary outcome of the study was the rate of canine retraction measured on three-dimensional (3D) digital models. Secondary outcomes were changes in canine tipping and root length that were assessed with CBCT scans, and the amount of first molar anchorage loss measured on the 3D digital models. The study was double blinded in which both the participants and the outcome assessor were blinded. Data were analyzed using ANOVA for the three groups. Paired sample t-test was used within each group. Results: A total of 32 canines were analyzed: 12 in G16, 10 in G17, and 10 in G19. The average distance moved by the canines per month was 0.9 ± 0.89, 0.68 ± 0.81, and 0.76 ± 0.98 mm in G16, G17, and G19, respectively, with no statistically significant difference between the three groups (P = 0.2). A statistically significant root resorption was observed in G19 compared to the other two groups (P = 0.024). Additionally, anchorage loss was greater in G17 and G19 compared to G16. A nonsignificant difference was detected between the three groups regarding the change in canine tipping. No harms were reported during the trial. Conclusions: Archwire sizes utilized in the current study showed no significant effect on the rate of canine retraction or tipping. However, wires with large sizes had more adverse effects with respect to root resorption and anchorage loss. Trial registration: The trial was registered at Clinicaltrials.gov with ID: NCT04020952. © The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature 2025.