Botulinum Toxin Versus Placebo Injections to Temporalis and Masseter Muscles

This study aims to determine whether the injection of botulinum toxin A or placebo (unpreserved 0.9% sodium chloride) into the masseter and temporalis muscles provides pain relief and improved jaw function in those who suffer from myofascial pain disorder. The study hypothesis is that botulinum toxin A injection is superior to placebo. The specific research questions are: 1. Is the injection of botulinum toxin A superior to placebo for the improvement in pain? 2. Is the injection of botulinum toxin A superior to placebo for the improvement in function or quality of life (QOL)? 3. Are there any adverse effects that result from injection of botulinum toxin A or placebo into the masseters and temporalis muscles? Limited data exists to support the use of botulinum toxin A in the management of myofascial pain disorder of the masticatory region. Botulinum toxin A is not FDA approved for intra-muscular injection within the masticatory region. Its use in the masticatory region is considered off-label but performed without significant known complications. This study will provide the opportunity to quantitate and qualitate any complications in a large prospective sample of patients.