Three-dimensional assessment of mini-implant supported maxillary canine retraction with and without power arm in class II division 1 patients: A split-mouth randomized trial

INTRODUCTION: The primary objectives of this trial were to compare the mechanics of direct sliding (DS) and power arm sliding (PAS) methods for canine retraction in regard to the rate of retraction, rotation, and tipping. The secondary objectives included the evaluation of canine mobility, mini-implant stability, and pain. MATERIAL AND METHODS: This split-mouth study was conducted over a 12-month intervention period on young adult patients with Class II Division 1 malocclusion requiring extraction of the maxillary first premolars, recruited between July 2023 and January 2024. Retraction methods were randomly assigned to sides by coin toss. Closed coil springs applying 150g retraction forces were stretched to the canine bracket hook on one side and the power arm on the contralateral side. Digital models were analysed to measure canine retraction rate, tipping, and rotation. Canine mobility and mini-implant stability were assessed with the periotest. The pain was evaluated using a visual analogue scale. Data were analysed using two-way mixed ANOVA, and intraclass correlation test. Blinding was only used during data analysis. RESULTS: Twenty patients (aged 18.35±2.85) were included. The total retraction rate was greater in DS (4.42±0.75mm) compared to PAS (2.93±0.56mm) with P<0.001. Tipping and rotation were significantly higher in DS compared to PAS with P<0.001, P=0.031, respectively. No statistically significant differences were observed between the 2 methods regarding mini-implant stability, and pain. However, canine mobility revealed a significant difference only during the first and second months (P=0.005, P=0.003, respectively) with higher periotest values recorded in the PAS group. No harm was observed during the trial. CONCLUSIONS: The DS method resulted in a faster rate of retraction than the PAS method. However, the PAS method effectively reduced both tipping and rotation, facilitating a more controlled bodily movement during canine retraction. Trial registration in Clinical-Trial.gov under identification number NCT06352996.