摘要： This split-mouth trial aimed to investigate the effect of low-level laser therapy (LLLT) on the amount of maxillary canine distalization when applied every 4 weeks over 12 weeks. Methods: Twenty-two adolescents and young adults (15 female, 7 male; aged 13-25 years; n 5 22) requiring bilateral maxillary first premolar extractions were recruited. After extractions and leveling-alignment, canines were retracted using closed-coil nickel-titanium springs delivering 150 g of force. LLLT was applied to 8 intraoral points on the buccal and palatal sides around the canine root for 10 seconds per point, on day 0, 28, and 56 with the control side receiving sham application. Alginate impressions were taken every 4 weeks on day 0, 28, 56, and 84. The amount of tooth movement, anchorage loss, and canine rotation were measured digitally. Randomization was through sequentially numbered, generated using www.randomisation.com and allocation concealment opaque, sealed envelopes. Participants, operator, and statistic assessor were blinded. Linear regression modeling accounting for clustering within each patient was used to identify differences between LLLT and control sides. Results: Twenty-one patients completed the study. The total amount of tooth movement was similar in the LLLT (2.55 6 0.73 mm) and control group (2.30 6 0.86 mm), whereas 0.25 mm (95% confidence interval, –0.21, 0.71 mm) of difference was insignificant (P 5 0.27). No significant differences were found for anchorage loss (P 5 0.22) or canine rotation (P 5 0.25). No harms were reported. Conclusions: Application of LLLT every 4 weeks did not result in differences in the amount of tooth movement, anchorage loss, and canine rotation during extraction space closure.