Effectiveness of Photobiomodulation for Myofascial Pain in Temporomandibular Disorders

Photobiomodulation in the Management of Myofascial Pain: A Randomized and Blinded Clinical Trial

This randomized clinical trial aims to evaluate the effectiveness of photobiomodulation therapy (PBM) alone or combined with therapeutic exercises compared with placebo PBM associated with exercises in patients with myofascial temporomandibular disorders (TMD). Participants will be allocated into three groups: PBM alone, PBM combined with exercises, or placebo PBM combined with exercises. The intervention consists of 12 treatment sessions. Outcomes related to pain intensity, mandibular function, and clinical measures will be assessed over time. The study seeks to investigate whether PBM provides additional benefits in pain reduction and functional improvement in individuals with myofascial TMD.

This randomized, assessor-blinded, parallel-group clinical trial aims to evaluate the effects of photobiomodulation therapy (PBM) on clinical and psychosocial outcomes in adults with myofascial temporomandibular disorders (TMD). Myofascial pain is one of the most prevalent subtypes of TMD and is frequently associated with muscle tenderness, functional limitation, chronic pain, and psychological distress. Conservative and non-invasive therapies are considered first-line approaches, and PBM has emerged as a promising modality due to its potential anti-inflammatory and analgesic effects.

The primary objective of this study is to analyze the impact of PBM on muscle pain intensity, assessed using the Visual Analog Scale (VAS). Secondary objectives include evaluating specific muscle pain through DC/TMD clinical examination, chronic pain severity using the Graded Chronic Pain Scale version 2 (GCS v2), mandibular functional limitation using the Jaw Functional Limitation Scale (JFLS-20), quality of life assessed using the Patient Health Questionnaire (PHQ-9), and anxiety symptoms using the Generalized Anxiety Disorder scale (GAD-7).

A total of 120 adult undergraduate and graduate students from the Federal University of Rio Grande do Sul (UFRGS) will be recruited through institutional dissemination and interest forms. Eligible participants must be 18 years or older, diagnosed with myofascial TMD according to DC/TMD criteria, and able to attend all treatment sessions and follow-up assessments. Individuals with systemic musculoskeletal conditions, recent head and neck malignancy, previous temporomandibular joint surgery, pregnancy or lactation, severe psychiatric conditions that prevent participation, or ongoing treatments that may interfere with outcomes will be excluded.

Participants will undergo baseline assessment and will be randomly allocated (1:1:1) into three groups: (1) PBM alone; (2) PBM combined with therapeutic exercises; or (3) placebo PBM combined with therapeutic exercises. PBM will be delivered using a dual-wavelength diode laser device (810 + 980 nm) applied extraorally at standardized anatomical points over the temporomandibular joint and masticatory muscles. The intervention will consist of 12 treatment sessions performed three times per week over four weeks. Participants allocated to the exercise groups will perform daily home-based therapeutic exercises focused on muscle relaxation, joint mobility, and functional improvement, with adherence monitoring throughout the study.

Randomization will be performed by an independent investigator using a centralized allocation system with concealment procedures. Participants will remain blinded regarding active or placebo laser application, and outcome assessors and statisticians will remain blinded to group allocation to minimize performance and detection bias. Due to the nature of the interventions, the therapist delivering PBM will not be blinded.

Clinical and psychosocial outcomes will be assessed at baseline, after completion of the 12 treatment sessions, and at 1-month and 3-month follow-up visits. Adverse events and rescue medication use will be monitored throughout the study period. Data will be managed using Research Electronic Data Capture (REDCap®) and analyzed under the intention-to-treat principle using mixed-effects statistical models to evaluate changes over time and between groups.

The study aims to provide high-quality evidence regarding the effectiveness of PBM alone or combined with therapeutic exercises in reducing pain, improving mandibular function, and positively influencing psychological outcomes in individuals with myofascial TMD, contributing to evidence-based conservative management strategies.

Inclusion Criteria:

• Individuals with myofascial TMD (ICD-9 729.1; ICD-10 M79.1) diagnosed according to the DC/TMD criteria;
• Participants aged 18 years or older;
• Individuals able to communicate, read, write, and provide written informed consent in Portuguese.

Exclusion Criteria:

• Patients with a history of autoimmune connective tissue diseases, such as rheumatoid arthritis, psoriatic arthritis, scleroderma, or systemic lupus erythematosus;
• History of malignancy in the head and neck region within the past 2 years (except basal cell carcinoma) who have undergone head and neck radiation therapy and/or surgery affecting facial muscles;
• Patients who have undergone temporomandibular joint surgery or orthognathic surgery;
• Pregnant or breastfeeding women;
• Patients with poorly adapted prostheses and/or prostheses associated with inadequate increase or decrease of the vertical dimension;
• Patients with a history of tardive dyskinesia or oromandibular/cervical dystonia; -Patients with maximum mouth opening less than 35 mm;
• Patients using systemic medications with a potential effect on pain at the time of screening will not be included in the study, including analgesics, anti-inflammatory drugs, muscle relaxants, corticosteroids, or other medications with analgesic and/or anti-inflammatory effects.

If a participant initiates the use of any such medication during the follow-up period, the participant will be excluded from the study.

- Patients receiving oral and/or intravenous corticosteroid bolus therapy at doses > 1 mg/kg within the past 3 months, and those receiving biologic agents within 1 month or five times the drug half-life, whichever is longer; Individuals with mental or psychological conditions that may prevent participation in the study.