Efficacy of Botulinum Toxin in Orofacial Disorders: A critical Review

Background: Botulinum Neurotoxin (BoNT), first recognized as a pathogen in the early 19th century, has evolved into a popular therapeutic agent. The known ability of BoNT to block acetylcholine release at neuromuscular junctions makes it useful in numerous muscular disorders, however new mechanisms of action, such as pain modulation, are still under investigation. In the past decade, new BoNT indications were discovered; several are under the jurisdiction of dentistry. Objectives: To critically review the current literature related to BoNT treatment in three oromandibular disorders: bruxism, oromandibular dystonia (OMD), and temporomandibular disorders (TMD) with or without orofacial pain (OFP), and to try establishing the effectiveness and safety of BoNT in their treatment. Methods: A search in the MEDLINE database for all articles since 2000 dealing with BoNT treatment for the disorders in focus. Articles were critically analyzed and significant issues highlighted in discussions. Results: The literature is mainly based on anecdotal case reports, or small-sample trials. Very few randomized controlled trials (RCT) were found. In the category of bruxism, 6 studies were reviewed, of which one was a small-sample RCT; all studies showed promising results. 9 studies on BoNT treatment for OMD were reviewed; none was an RCT, although two employed large sample sizes. Most of the subjects showed improvement; however, a few case reports demonstrated the phenomenon of loss of response to BoNT after several treatments. 20 articles regarding the effectiveness of BoNT for the treatment of TMD with or without orofacial pain were found; all studies but one presented positive outcomes. Conclusions: While it seems that BoNT has a promising therapeutic potential for all three disorders, the need for further investigation is obvious. Currently, there is not enough literature to estimate the therapeutic value of BoNT in bruxism, OMD, and TMD with or without orofacial pain.