Evaluation of the Effects of Low-Level Laser Therapy on the Rate of Relapse of Mandibular Incisors after Fixed Orthodontic Treatment: A Randomized Controlled Trial

Background and Objective: Stability is one of the major issues in orthodontics. The purpose of this study is to investigate the effect of Low-Level Laser Therapy on the rate of relapse of mandibular incisors. Methods: This Single-blinded Randomized Controlled Trial consisted of twenty patients (aged 12-18 years) seeking orthodontic treatment. The subjects were divided into two groups with randomly permuted blocks (n=10): experimental and control groups. The Little’s irregularity index was measured on plaster models prior to treatment using American Board of Orthodontic Measuring Gauge. After unraveling of initial crowding, archwires on mandibular anterior segments of both groups were removed. The experimental group received Low-Level Diode Laser at 808 nm wavelength, 250 mW power, 4J energy and continuous wave mode, on coronal third of lower central and lateral incisors and canines’ roots for sixteen seconds three times a week, within a four-week period. The relapse rate was quantified on each plaster model using Little’s irregularity index at the end of first (T1), second (T2), third (T3), and fourth (T4) weeks. Findings: The study population consisted of twenty patients aged 12-18 years who had 5-9 mm crowding and proper oral hygiene. At T1, the relapse rate was 0 mm and 0.05±0.15 mm in experimental and control group, respectively, which was not statistically significant (p=0.343). Over the following weeks, however, there was statistically significant difference between the relapse rate of the two groups (p=0.003). The mean rate of relapse percentage was 4.48±4.31 mm in experimental and 12.06±5.52 mm in control group, which was significantly lower in Low-Level Laser Therapy group. Conclusion: The application of Low-Level Laser Therapy at 808 nm wavelength on mandibular incisors during orthodontic retention phase may slow down the relapse rate. Therefore, it could be considered as an effective adjunct to reduce immediate relapse.