Botox injections to manage jaw and facial pain do not result in clinically significant changes in jawbone when used in the short term and in low doses, according to researchers at the New York University (NYU) College of Dentistry. However, they did find evidence of bone loss when higher doses were used.
The researchers are now calling for further clinical studies to track bone- and muscle-related changes with long-term use of Botox for temporomandibular muscle and joint disorders (TMJDs).
TMJDs are a group of common pain conditions that occur in the jaw joint and surrounding muscles. The most common involve the muscles responsible for chewing. While many people manage their TMJD symptoms with conservative treatments such as jaw exercises, oral appliances, dietary changes, and pain medication, some do not respond to these treatments.
Known for its wrinkle-reducing capabilities, Botox (or botulinum toxin) is an injectable drug approved by the Food and Drug Administration to treat certain muscle and pain disorders, including migraines. It works in part by temporarily paralyzing or weakening muscles.
In the United States, a Phase 3 clinical trial is currently underway to study the use of Botox to treat TMJD, but in the meantime, it is increasingly being used off-label. Thus fa, small studies using Botox to treat TMJD in human beings have had mixed results, the researchers said.
In animal studies, Botox injections in jaw muscles have led to major bone loss in the jaw. This is thought to be due to the muscles not being used to exert force needed for bone remodeling, but Botox may also have a direct effect on bone resorption, the process of breaking down bone tissue, the researchers said.
“Given these concerning findings from animal studies, and the limited findings from clinical studies, more research on the safety of Botox for jaw muscles and bones is critically important,” said Karen Raphael, PhD, MS, MA, professor in the Department of Oral and Maxillofacial Pathology, Radiology and Medicine at the NYU College of Dentistry and the study’s lead author.
The study comprised 79 women with TMJD affecting their facial muscles, including 35 who received Botox injections (between two and five rounds in the previous year) and 44 who were not treated with Botox but may have used other TMJD treatments. Using specialized CT scans, the researchers measured participants’ jawbone density and volume.
The researchers found that jawbone density and volume were similar between women who had Botox injections to treat their TMJD and those who did not. While most participants were given relatively low doses of Botox, smaller than in most clinical trials for TMJD, individuals who received higher doses of Botox were more likely to have lower bone density.
The researchers recommend that more human studies be conducted to better understand the impact of the long-term use of Botox on jaw muscles and bones and whether it just reduces muscle force on bone or also plays a direct role in altering bone resorption.
“Should Botox receive regulatory approval for the treatment of TMJD, we would recommend that a Phase IV study be done using low-radiation CT and MRI to track bone- and muscle-related changes with Botox use, examining both dose and long-term use,” said Raphael.
“Unless specialized imaging of muscle and bone are conducted among patients who receive Botox treatment over long periods, true cumulative effects will remain unknown,” said Raphael.
The study, “Effect of Multiple Injections of Botulinum Toxin into Painful Masticatory Muscles on Bone Density in the Temporomandibular Complex,” was published by the Journal of Oral Rehabilitation.
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