IRCT2016051527894N2 IRCT 2017-04-26 Vice chancellor for research of Ahvaz Jundishapur University of Medical Sciences comparison of the effect of botulinium toxin A injection with placebo in reducing the pain of patients with myofacial pain Evaluation of the effect of botulinum toxin type A injection for reducing the pain in patients with myofascial pain 2016-03-20 anticipated 34 Complete https://irct.ir/trial/22758 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Crossover, Purpose: Treatment. N/A temporomandibular disorder. Intervention 1: Intervention: Patients in intervention group will receive 150 units of botulinium toxin A (diluted in 1 cc normal saline) which will be injected in several points on masseter and temporalis muscles and they will be followed up at the first and fourth months after intervention, then at the fifth month after intervention they receive 1 cc normal saline which will be injected in the same sites, then they are again followed up at the first and fourth months after placebo treatment. Intervention 2: Control: The patients in placebo group firstly will receive 1 cc of normal saline which will be injected in several points on masseter and temporalis muscles, then they are followed up at the first and fourth months after placebo treatment then at the fifth month after receiving normal saline, they will receive 150 units of botulinium toxin A (diluted in 1 cc of normal saline) at the same sites and again are followed up at the first and fourth months after injection.