Unclear results for the use of botulinum toxin therapy for TMD pain

A comprehensive search was carried out on major databases such as PubMed, EMBASE and Cochrane CENTRAL. Reference lists of the included studies were explored along with journals likely to contain studies relevant to the topic. The search was restricted to the English language.

The inclusion criteria included randomised and quasi-randomised controlled trials including parallel or cross-over studies comparing botulinum toxin therapy (BTX) versus any alternative intervention or placebo.

Quality assessment and data extraction were done following the Cochrane risk of bias tool and recommendations. All of the steps in the review, including the search and selection process, were done independently by two reviewers. Disagreements were discussed with one another until consensus was reached.

Five relevant studies were included in the review, which consisted of 117 participants. Two trials revealed a significant inter-group difference in myofascial pain reduction. Another trial that compared BTX with fascial manipulation showed no significant difference in pain relief for temporomandibular disorders (TMDs), while the remaining two trials showed no significant difference between the BTX and placebo groups. Meta-analysis was not performed due to the considerable variation in study methods and evaluation of the results. All five studies were targeted primarily on the masseter and temporalis muscles and most of them administered injections at bilateral muscle sites. The methods used to find the muscles to target were all based on physical examination, with three studies using electromyography (EMG) as guidance. The dose of BTX ranged from 70U to 300U, the majority used being 100-150U. All studies gave a single session of BTX and re-evaluated participants at least one month following the injection.

No consensus could be reached on the therapeutic benefit of BTX on TMDs.