Peripheral TMD Pain Mechanisms and the Effect by Botulinum Toxin A

The goal of this clinical trial is to investigate the effect of botulinum toxin on neurons' plasticity in the masseter muscle in humans with and without painful myogenous temporomandibular disorders (TMDM). The main questions it aims to answer are:does treatment with botulinum toxin alter gene expressions, epigenetic signatures, and cells plasticity in the masseter muscles of TMDM patients?do any such changes differ between patients with local and regional TMDM?does treatment with botulinum toxin influence pain characteristics (intensity, frequency, and sensibility) and other variables in patients with TMDM and are there correlations between significantly changed expression of biomarkers and other variables? Participants will be examined with a questionnaire, clinical examination, and biopsy sampling from one of the masseter and are then randomized to treatment with botulinum toxin or control (isotonic saline). Follow-ups occur after one, three, and six months with questionnaire, clinical examination, and collection of post-treatment microbiopsies to see if botulinum toxin alter peripheral molecular events and clinical variables.

Inclusion Criteria:a diagnosis of TMDM myalgia or myofascial pain according to the DC/TMD criteriafemales with adequate contraceptives and a negative pregnancy testpain upon digital palpation of at least one of the masseter musclea characteristic pain intensity of > 40/100.Exclusion Criteria:difficulties understanding the Swedish languagesystemic inflammatory connective tissue diseaseswidespread painneuromuscular disordersdiagnosed or severe psychiatric diseaseneuropathic painpain of dental originhistory of trauma to the face, head or neckpregnancy or nursingknown allergy to botulinum toxin or antibioticsuse of muscle relaxants, antidepressant, neuropsychiatric, anticoagulant drugs, or aminoglycoside antibioticsprevious treatment with botulinum toxin during the last 12 monthsuse of analgesic or anti-inflammatory medication during the 48 hours preceding biopsyskin infection over injection/biopsy site