This study will be implemented on 20 patients referring to Department of Prosthetic Dentistry of Mashhad Dental School. The patients are selected according to the RDC/TMD criteria to include those having temporomandibular disorders with muscular origin. The patients will be randomly assigned to two groups: Group 1 (treatment group) will receive low level laser therapy. The laser light will be applied with 890 nm diode laser (Mustang 2000+, Russia) with frequency of 1500 Hz, and dose of 2 J/cm2 per point in the painful muscles.