Effectiveness of Physical Methods in Accelerating Upper Canine Retraction: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

TL;DR

This study reviews how physical methods like laser therapy and vibration can speed up orthodontic treatment for upper canine retraction.

Contribution

The paper provides a systematic review and meta-analysis comparing the effectiveness of physical methods in accelerating upper canine retraction.

Findings

Low-level laser therapy increased retraction rate by 0.43 mm/month.

Mechanical vibration increased retraction rate by 0.36 mm/month.

No significant adverse effects were observed with these methods.

Abstract

Orthodontic treatments for maxillary canine retraction often extend over long durations, affecting patient comfort and compliance and leading to growing interest in using physical modalities such as low-level laser therapy (LLLT), mechanical vibration, and electromagnetic fields to accelerate tooth movement. This study systematically evaluates and compares the effectiveness of these physical methods in increasing the rate of upper canine retraction in fixed-appliance orthodontic patients.

A comprehensive electronic search of six databases was conducted through July 5, 2025, to identify randomized controlled trials (RCTs) evaluating LLLT, mechanical vibration, or electromagnetic interventions for maxillary canine retraction. Eligible studies compared these modalities with standard orthodontic controls and reported the rate of upper canine retraction (mm/month) as the primary outcome, alongside secondary outcomes including canine angulation, rotation, anchorage loss, and root resorption. Risk of bias was assessed using the Cochrane RoB2 tool, and meta-analyses were performed to calculate mean differences (MDs), p-values, and heterogeneity (I²).

Sixteen RCTs with 322 participants were included, revealing that LLLT significantly increased the retraction rate (MD = 0.43 mm/month, p = 0.007; I² = 97%), which, after sensitivity analysis, became MD = 0.26 mm/month (I² = 48%). Mechanical vibration also significantly increased retraction (MD = 0.36 mm/month, p < 0.00001), with no heterogeneity (I² = 0%). Evidence for electromagnetic fields was limited but still positive. For secondary outcomes, no significant adverse effects were noted for angulation, rotation, anchorage, or root integrity, although one study reported minimal, nonsignificant root resorption.

In conclusion, physical modalities - particularly LLLT and mechanical vibration - can moderately accelerate upper canine retraction without detectable adverse effects. However, due to variability in protocols and limited long-term data, further high-quality RCTs with standardized methodologies are warranted before routine clinical application.

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