This study aims to evaluate whether intramuscular injections of platelet-rich plasma (PRP) are more effective than isotonic saline in reducing pain and improving jaw function in individuals diagnosed with myogenous temporomandibular disorders (TMD). Myogenous TMD is a common source of orofacial muscle pain and functional limitation, and although conservative treatments help many patients, a significant proportion continue to experience persistent symptoms that affect daily life and quality of function.

PRP is an autologous, minimally invasive biologic concentrate enriched with platelets and bioactive molecules that may promote tissue repair and modulate inflammation, making it a promising option for managing muscle-related pain conditions. However, evidence from well-controlled randomized clinical trials in myogenous TMD remains limited.

In this double-blind, randomized controlled clinical trial, participants will receive two intramuscular injections-either PRP or saline-administered one month apart. Follow-up assessments will occur at 1, 3, and 6 months using standardized and validated measures of pain intensity, pain sensitivity, mandibular function, and psychosocial factors.

The results of this study may help determine the clinical value of PRP for myogenous TMD and contribute to future standardization of regenerative treatment protocols in orofacial pain management.

Inclusion Criteria:

• for the experimental part of the project are: women 20 to 50 years with a confirmed diagnosis of myogenous TMD according to the DC/TMD (21). Participants must have pain in the masticatory muscles. Pain duration must be at least 3 months. Participants must report current pain at the day of inclusion with a minimum score of 4 on the numeric rating scale (NRS 0 to 10).

Exclusion Criteria:

• active infection or inflammation at the injection site, systemic infection, platelet or coagulation disorders, severe anemia, autoimmune or inflammatory rheumatic disease, chronic liver disease, uncontrolled diabetes, or active malignancy. Pregnancy or breastfeeding will also be exclusion criteria. Patients using anticoagulant or antiplatelet medication that cannot be temporarily discontinued, or receiving chronic corticosteroid or immunosuppressive therapy, will be excluded. Additional exclusion criteria include predominantly arthralgia temporomandibular disorders, previous temporomandibular joint surgery, or a history of significant trauma to the face, head, or neck, including orthognathic surgery. Patients will also be excluded if they present widespread pain conditions such as fibromyalgia, neuromuscular disorders such as craniomandibular dystonia or myasthenia gravis, diagnosed or severe psychiatric disease such as schizophrenia or bipolar disorder, neuropathic pain, or pain of dental origin. Patients unable to provide informed consent or complete study questionnaires will be excluded.