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The Scoop on TMD Pharmaceuticals

Let's say the National Institutes of Health just handed us a multi-million dollar grant to get to the bottom of TMD and find a cure once and for all. I mean, we could start handing out heating pads left and right, but that kind of relief can only get us so far. Whenever I try a different form of therapy or medication, I like to think about the biology, right down to the cellular and molecular level. Why are the cells that make up my jaw region being such jerks?

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The TMJ Association is pleased to partner with Inspire to bring you the TMJ Cafe, a free online support network and discussion community for those with Temporomandibular Disorders (TMD). We invite you to meet others like you, share experiences and tips for getting through the day, and give and receive support.

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.

Repeated Injections of Botox into the Masseter Muscle... A Longitudinal Study

  • Oct 5, 2017

We thank Dr. Susan Herring for writing the following article summary.

Lee HJ, Kim SJ, Lee KJ, Yu HS, Baik HS. Repeated injections of botulinum toxin into the masseter muscle induce bony changes in human adults: A longitudinal study.   Korean J Orthod. 2017 Jul;47(4):222-228. 

The authors of this study examined mandibular bone before and after subjects received Botox injections into each masseter muscle. These volunteers were healthy adults (22-48 years old), both male and female, who wanted injections to slim their faces. (This happens because the Botox causes temporary muscle paralysis and the masseters undergo atrophy when they are not used.) The 20 subjects were randomized into two groups. One group received a single dose of Botox in each muscle while the second group got two doses. The second dose was given 4 months after the first. The bone scans were cone-beam computed tomography (CBCT), a 3-D technique with relatively low radiation. The after-Botox CBCT scan was performed 6 months after the initial injection. The scans were directed at the mandibular angle, where the masseter attaches. The TMJ region was not examined.

Even 6 months after a single injection, the masseter muscles were much smaller than before injection (loss of about 70 mm2). Predictably, the shrinkage was much greater for the two-injection group (loss of about 140 mm2).

The very limited amount of mandibular bone examined is only part of the masseter's attachment, and an unaffected muscle, the medial pterygoid, attaches to it as well. Therefore, it is surprising that the authors were able to document a loss of bone volume which was statistically significant in the 2-injection group. The loss was due to thinning of the bone, because the mandible as a whole did not become smaller. The authors refer to this finding as an "unwanted side effect" of multiple Botox injections of the masseter muscles.

This study was not ideal and leaves many questions unanswered. Sample size was small, there were no uninjected control subjects, differences between the groups at the start were not reported, the bone examination was very restricted, and it is unknown whether full restoration of muscle and bone would eventually have occurred.  

Nevertheless, it is the first prospective, randomized, longitudinal study of the effects of Botox on the human jaw. The finding of bone loss is consistent with the only other human Botox study on jaws, a cross-sectional examination of the condylar bone of TMJ disorder patients who did or did not receive masseter injections (Raphael et al. 2014). The paper by Lee et al. reinforces the idea that thinned and weakened jaw bones are likely side effects of Botox treatment.

 Raphael, K. G., A. Tadinada, J. M. Bradshaw, M. N. Janal, D. A. Sirois, K. C. Chan and A. G. Lurie (2014). Osteopenic consequences of botulinum toxin injections in the masticatory muscles: a pilot study. J Oral Rehabil 41: 555-563.

Read the full article: https://synapse.koreamed.org/Synapse/Data/PDFData/1123KJOD/kjod-47-222.pdf

TMJ Disorders

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