The investigators set up a randomized controlled clinical trial to evaluate the effectiveness of plasma rich in growth factors (PRGF) injections into the masseter muscle trigger points for myofascial pain treatment. The investigators also seek to compare PRGF injections effectiveness with local anesthetic injections.

Dry needling and local anesthetics injections release trigger point by disrupting the membranes of a tout band. However, the injected substance itself does not affect the pathophysiological mechanism of the trigger point.

It is known that the platelets release growth factors who can enhance muscle regeneration processes and moreover reduce chronic pain.

The investigators raised a hypothesis that PRGF injections into the trigger points in masseter muscle can be an effective treatment method for the myofascial pain.

Inclusion Criteria:

• Adult patients.
• Diagnosed myofascial pain syndrome in one side of the masseter muscle (diagnosis is based on diagnostic criteria described by Travell and Simons: 1) palpable taut band, 2) spot tenderness in a taut band, 3) pain recognition.
• Patients have never had injections into their masseter muscle.

Exclusion Criteria:

• Myofascial trigger points in other masticatory muscles.
• Head and neck region inflammations that causes pain.
• Temporomandibular joint pathology which causes pain.
• Trigeminal nerve neuralgia.
• Head and neck region oncological diseases.
• Myofascial trigger points in both sides of masseter muscles.