Myofascial pain dysfunction syndrome is one of the common causes of non-odontogenic pain in the head and neck region. It accounts for 40-60% of the adult population. Different treatment modalities had been reported to release the trigger point within the muscles of mastication in order to reduce pain and allow recovery of the function.

Low-level laser therapy has been a research focus in past few years as it provides effective and conservative treatment modality with minimal patient discomfort. LLLT promotes the release of endogenous opioids, enhance tissue repair and cellular respiration, increase vasodilatation and pain relief Recent systematic review and meta-analysis had reported that the available evidence didn't allow clinicians to draw firm conclusions on effective dosage. This study aimed to investigate the effect of different LLLT sessions' number on pain, maximum mouth opening and quality of life in patients with masseter muscle trigger points.

Inclusion Criteria:

1. definite diagnosis of myofascial pain based on the DC/TMD criteria with a referral
2. presence of one or more trigger points in the masseter muscle
3. no history of any invasive procedures of the related masseter muscle.

Exclusion Criteria:

1. any painful conditions affecting the orofacial region
2. any systemic diseases that could masticatory function (e.g., rheumatoid arthritis and epilepsy)
3. pregnancy and lactation.