Efficacy of photobiomodulation therapy using 980 nm versus 635 nm diode lasers for treatment of myofascial pain : a randomized controlled trial

Myofascial pain syndrome (MPS) is a common musculoskeletal disorder characterized by myofascial trigger points and muscle dysfunction. Photobiomodulation therapy (PBMT) with diode lasers has shown promise for analgesia and functional improvement in MPS management. This study compared the efficacy of 635 nm and 980 nm diode lasers in alleviating pain and enhancing mandibular function in MPS patients. Thirty patients were randomized into two groups Group A (635 nm, 0.5 W, 60 s, 38.2 J/cm²) and Group B (980 nm, 0.2 W, 60 s, 15.3 J/cm²), applied twice weekly for five weeks. Outcomes included visual analogue scale (VAS), Maximum Mouth Opening (MMO), lateral/protrusive movements (LM/PM), and surface electromyography (sEMG) at baseline, post-treatment, and one-month follow-up. Both groups showed significant improvements in all outcome measures (p < 0.001). VAS decreased from 7.6 ± 1.2 to 2.9 ± 1.3 (≈ 62% reduction) in the 635 nm group, and from 7.8 ± 1.1 to 2.1 ± 0.9 (≈ 73% reduction) in the 980 nm group (between-group p = 0.02). Maximum Mouth Opening (MMO) increased by 7.6 mm (34.5 ± 4.2 → 42.1 ± 3.2) in the 635 nm group versus 10.2 mm (34.0 ± 3.9 → 44.2 ± 2.9) in the 980 nm group (p = 0.01). Lateral movement (LM) improved by 2.3 mm vs. 2.8 mm, and Protrusive movement (PM) improved by 1.7 mm vs. 2.1 mm in the 635 nm and 980 nm groups, respectively. sEMG showed greater muscle activity reduction with 980 nm vs. 635 nm (Masseter: 47–51% vs. 39–40%; Temporalis: 43–44% vs. 36%; see(Table 3 for full data). PBMT with 980 nm produced superior pain relief, muscle relaxation, and Mandibular function recovery compared to 635 nm, likely due to deeper tissue penetration. However, interpretation should consider the small sample size and lack of placebo control. ClinicalTrials.gov, NCT07069764. Registered retrospectively on 07 July 2025.