Clinical Effectiveness of Muscle Relaxants and Paralytics in the Treatment of Temporomandibular Disorders: A Systematic Review of the Literature

Introduction: Temporomandibular dysfunction is a benign pathology, with polymorphic expression and subject to multiple factors that participate in its etiology, which makes the diagnosis of certainty difficult. A wide range of therapeutic options are available, including splints, physical therapy, pharmacotherapy (analgesics, muscle relaxants, anxiolytics, antidepressants, etc.)

Objective: The aim of our work is to conduct a systematic review evaluating the clinical efficacy of muscle relaxants and paralyzers in the treatment of temporomandibular disorders in the light of Evidence Based Dentistry.

Methods: The collection of data from the scientific literature was carried out among the production that appeared during the period from 2000 to 2021. The literature search was carried out by exploiting databases accessible via the Internet, namely Medline through its search engine Pubmed, Elsevier, Google scholar, Research for life and Web of science. A bottom-up manual search covering the same study period was carried out in order to expand our bibliography. The writing of this systematic review followed the guidelines of PRISMA Statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).

Results: 9 relevant articles were retained after critical reading guided by CASP-type reading grids. The articles were then classified into 3 categories according to the type of molecule administered:
-Administration of centrally acting muscle relaxants
-Administration of anxiolytics with muscle relaxant properties
-Administration of muscle paralyzer
The articles were classified in tables according to the PICO criteria (Participants/Interventions/Comparison/Outcomes). The results of our study showed a decrease in pain intensity after administration of muscle relaxants and anxiolytics with muscle relaxant properties. Botulinum toxin injection also has the advantage of being a minimally invasive procedure and an effective treatment method in patients who do not respond to the most conservative treatments.

Discussion: The results of our studies regarding the efficacy of muscle relaxants and paralytics in the management of temporomandibular disorders are supported by other systematic reviews and meta-analyses. However, new research with a longer observation period, a large sample size and a correct methodology is still needed.

Conclusion: The disparity of the results of the studies and the absence of scientific evidence that would lead to a consensus on the efficacy of muscle relaxants and paralytics in the treatment of TMD do not allow for clear-cut conclusions. In addition, the small size of the populations studied makes it impossible to extrapolate the results, which is why more in-depth studies are needed.

Keywords: Temporomandibular joint disorders, Neuromuscular agents, Cyclobenzaprine, Botulinum toxins