The Effect of Low-Level Laser Therapy to Reduce Pain Caused by Orthodontic Separators: A Randomized, Double-Blind Placebo-Controlled, Split-Mouth Study

<b>Background:</b> During the initiation of routine orthodontic treatment with fixed appliances, placing elastic separators (ESs) may lead to the patient experiencing considerable pain. Earlier studies evaluating the effects of low-level laser therapy (LLLT) on reducing pain caused by orthodontic ESs have reported contradictory results. The aim of our study was to evaluate the effect of a single application of LLLT on the experience of pain following ES placement. <b>Methods:</b> A double-blind, placebo-controlled randomized controlled trial was performed-with implementation of the split-mouth technique-where <i>n</i> = 33 volunteers (12 male and 21 female; aged between 19 and 36 years) were enrolled. ESs were placed at the mesial and distal surfaces of the first permanent molars in the upper or lower jaws. Jaws were divided into two quadrants; the treatment group received LLLT (using a GaAlAs diode laser, at a 980 nm wavelength, with 100 mW producing 6 J of energy; continuous wave), while the other quadrant served as the placebo side receiving a similar treatment, but without laser irradiation, immediately after separation. A questionnaire with a visual analogue scale (VAS; 0-100) was used for the assessment of pain (spontaneous pain and pain on mastication) scored for each first permanent molar directly after separation and after 6, 24, 48 and 72 h of both laser and placebo treatment application. <b>Results:</b> Mean VAS values were lower, but not significantly different, between the treatment vs. placebo groups for spontaneous pain at either measurement point (<i>p</i> > 0.05). Mean VAS values were significantly lower in the treatment groups for pain on mastication at the 6 (9.29 ± 12.65 vs. 19.07 ± 20.99; <i>p</i> = 0.025), 24 (21.96 ± 21.11 vs. 37.19 ± 26.35; <i>p</i> = 0.012) and 48 h (28.01 ± 21.40 vs. 42.60 ± 26.29; <i>p</i> = 0.016) measurement points. The analgetic effect of LLLT was most effective after 6 h, both in the resting position (-49% decrease) and during mastication (-51% decrease). <b>Conclusions:</b> A single application of LLLT with 6 J of energy may have beneficial effects on reducing the pain caused by orthodontic ESs used at the initiation of treatment with fixed appliances, especially during mastication, after 6-48 h following the separation procedure. <b>Trial registration:</b> clinicaltrials.gov ID NCT06816537 (date of registration: 7 February 2025, retrospectively registered).