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Sustained and Repeated Mouth Opening Leads to Development of Painful Temporomandibular Disorders Involving Macrophage/Microglia Activation in Mice

Temporomandibular disorder (TMD) is a set of heterogeneous musculoskeletal conditions involving the temporomandibular joint (TMJ) and/or the masticatory muscles. Up to 33% of the population has had at least one symptom of TMD with 5-10% of them requiring treatment. Common symptoms include limited jaw movement, joint sound, and pain in the orofacial area. Once TMD becomes chronic, it can be debilitating with comorbidities that greatly reduce one's overall quality of life. However, the underlying mechanism of TMD is unclear due to the multicausative nature of the disease.

Prevalence of TMD in Sjӧgren Syndrome Patients

Sjӧgren's Syndrome seems to play a role in temporomandibular joint disorders.

Early Molecular Response and Microanatomical Changes in the Masseter Muscle and Mandibular Head After Botulinum Toxin Intervention in Adult Mice

The Botox-injected masseters had greatly increased expression of genes involved in muscle atrophy at the 1 week time point compared to the control side muscles. At the end of the study, 2 weeks after injection, the Botox-injected masseters were about 20% smaller than the control side masseters, and the Botox-side condyles had lost about 40% of relative bone area compared to the control side condyles.

Centralized Pain in TMD: Is It All in the Head?

We are pleased to introduce Sophia Stone, a new contributor to The TMJ Association, whose passion is to separate TMD fact from TMD fiction. Sophia has a background in medicine and research and can draw on her personal experience as a TMD patient.

Is Botox Safe and Effective for TMD?

  • Sep 24, 2014

As TMJ patients search for alternative treatments to manage their pain, a doctor may have suggested the possibility of trying Botox injections directly into the chewing (masseter and temporalis) muscles to relax these muscles. In addition to its well-publicized cosmetic uses, Botox has been approved by the FDA for painful conditions potentially related to TMJ, such as cervical dystonia and migraine. Of note, Botox is not FDA-approved for use in TMJ disorders. When doctors offer this treatment to TMJ patients, patients should be aware that this is "off-label use" that is not approved by the FDA. The FDA has not evaluated the safety or efficacy of this powerful neurotoxin for TMJ pain treatment. Adding to the uncertainty about whether to pursue treatment of TMJ pain with Botox , clinical trials published so far have been small and have produce inconsistent findings.
 

Before we ask whether Botox can help reduce your TMJ pain, we need to ask a more basic question: Is it safe to use Botox this way? When injected into muscles, Botox causes a partial paralysis of those muscles. The paralysis changes the forces causing normal stress on the TM joint. These forces are considered necessary to maintain the usual process of breakdown and regrowth of bone. If the paralysis changes bone remodeling in the TMJ area, injection of Botox into the chewing muscles might cause unique safety concerns and unknown long-term problems.

 

In an important first step to addressing these concerns, Dr. Susan Herring and her colleagues at the University of Washington in Seattle examined the effect of Botox injections into the jaw muscles of rabbits. In the August 2011 issue of TMJ News Bites, Dr. Herring summarized her findings. She concluded "Botox in the masseter caused an osteoporotic condition in the TMJ of rabbits, raising some concern that this treatment might not be healthy for the joint in the long term."

 

These findings indeed raised concerns, but it was unclear whether findings from a rabbit study had relevance for humans. With the cooperation of the TMJ Association, Dr. Karen Raphael and colleagues at New York University posted an online survey on the Association's website, to identify women who had received TMJ injections in their chewing muscle and a similar group of TMJ patients who did not. Among the 150+ women who completed the survey, Dr. Raphael and colleagues invited a small group of well-matched Botox recipients and nonrecipients, all with TMJ pain, to participate in a study intended to determine whether Dr. Herring's animal findings had relevance for humans. Ultimately, as published in the May 2014 issue of the Journal of Oral Rehabilitation, 7 women who had been treated with Botox for their TMJ pain and 9 matched women who had never received Botox underwent specialized radiological imaging of their TMJs. The images were evaluated by oral and maxillofacial radiologists who did not know their treatment history. The radiologists found abnormally low bone density in the TMJ area in all of the women treated with Botox and in none of the women who did not receive Botox .

 

These findings indicated that more research on the safety of Botox for TMJ pain treatment is essential, to guide both patients and health care providers. We are happy to report that the National Institutes of Dental and Craniofacial Research (NIDCR) of the NIH has provided a grant to Dr. Raphael's team to conduct a much larger study addressing the safety of Botox treatment. If it is found to be a safe treatment when injected in the chewing muscles then, and only then, we can we address broader questions of whether it actually helps reduce the pain of TMJ disorders.

 
Additional Resource: Raphael, K. G., Tadinada, A., Bradshaw, J. M., Janal, M. N., Sirois, D. A., Chan, K. C. and Lurie, A. G. (2014), Osteopenic consequences of botulinum toxin injections in the masticatory muscles: a pilot study. Journal of Oral Rehabilitation. doi: 10.1111/joor.12180 
 
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TMJA1 - Thursday, July 17, 2014
I found the report by Dr. Raphael about studies that seem to show the potential of Botox injections into the masticatory muscles to treat myofascial pain causing decreased bone density in the temporomandibular joint very informative. However, it is important for patients to understand that there are also other reasons why one should be cautious about having such injections (1). It has been shown that some patients who received multiple Botox injections into the temporalis muscle for the treatment of headaches developed so-called disuse atrophy (wasting or loss of muscle tissue), resulting in a disfiguring depression on the side of the head (2). In fact, this adverse effect of Botox injections has actually been used to treat masseteric hypertrophy (bulging masseter muscles), so it could also occur in patients with myofascial pain who have normal-shaped masseter muscles. Secondly, some patients may develop an immune response (antibodies) to Botox that would then block its action and make the injections ineffective. Finally, and perhaps most importantly, such injections are being used to treat the symptoms of myofascial pain but not the cause of the problem, which is an illogical way to approach this situation. Daniel M. Laskin DDS, MS Clinical Advisor, The TMJ Association 1. Botulinum toxin A in the treatment of myofascial pain and dysfunction: the case against its use. Laskin DM. Oral Maxillofac Surg 70; 1240-1242, 2012. 2. Hourglass deformity after botulinum toxin type A injection. Guyuron B et al. Headache 44; 262, 2004.