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

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.

Washington Post Article on TMD

The Washington Post recently featured an article on Temporomandibular Disorders. Below is an excerpt from that article and a link to the full story.

Partnering to Improve Chronic Pain Care

The National Institutes of Health (NIH) held three meetings this summer with the goal of developing the first public-private partnership (PPP) to develop safe and effective treatments for chronic pain, as well as new treatments for opioid addiction and overdose.

TMJ Patient RoundTable Project: Status Update

The TMJ Association is acting as the catalyst to develop the TMJ Patient RoundTable, a broad initiative to advance the interests of patients with temporomandibular disorders (TMD). It encompasses collaborations with all stakeholders and

Educational Brochures on Chronic Overlapping Pain Conditions

This brochure addresses what are Chronic Overlapping Pain Conditions (COPCs), how COPCs are diagnosed, the complexity of the chronic pain experience, and how to work with your health care provider to develop a treatment plan. It is available by postal ma

Are TMD Patients More Pain Sensitive? Maybe. But It's Complicated

  • Dec 16, 2016

TMD patients come in many different varieties. Some experience pain and dysfunction confined only to the jaw and/or the associated chewing muscles. Other TMD patients have jaw pain plus one or more other painful conditions elsewhere in the body. Scientists have been trying to figure out if these differences in their experience of pain reflect any long-term changes in the brain, in particular a phenomenon called "central sensitization," in which individuals become more sensitive to pain over time. Although "central sensitization" is considered a normal phenomenon, pain sensitive individuals may have brain changes that may make their pattern of central sensitization different than that of individuals without chronic pain.

To test for central sensitization, researchers typically use a 'temporal summation' method, in which volunteers are exposed to a nonpainful stimulus that becomes painful with repeated exposures to it. You might make an analogy to water dripping on rock that over time eventually penetrates the rock. In the temporal summation method used in the TMD experiment described below, volunteers were exposed to a heated pad placed on their palms for multiple times over a fixed time period. Individuals experiencing central sensitization would feel the heated pad becoming painful over time.

It is widely believed that individuals with fibromyalgia (widespread pain with diffuse tender points that are painful when lightly pressed) and perhaps some other pain conditions, including TMD, experience enhanced central sensitization, demonstrated either by reaching peak pain earlier in the temporal summation test or perhaps by having more lasting 'aftersensations' following removal of the heat. In a study conducted at New York University by Dr. Karen Raphael in collaboration with other institutions, researchers compared experimental pain sensitivity in three groups: patients with only muscle-based TMD (n=100), patients with TMD plus fibromyalgia (n=26), and a matched pain-free control group (n=48). Their surmise was that the TMD patients with fibromyalgia would have different pain sensitivity than TMD patients whose pain was confined to the chewing muscles or normal controls.

Results: Surprisingly, when the researchers looked at each individual participant, temporal summation did not often occur as expected, and rates of summation did not differ among participants in different groups. Even at the highest constant temperatures considered safe to test, less than half of participants showed an increase in subjective painfulness of the heated pad over repeated presentations. Participants were more likely to either rate the heat as having a consistent painfulness over time or, for some, even a reduction in painfulness. Examining just those participants who appeared to become centrally sensitized, the rate and pattern of central sensitization did not differ among any of the study groups. However, the subgroups of TMD patients had longer-lasting painful aftersensations than controls when the heated pad was removed. TMD patients with fibromyalgia had similarly painful aftersensations to those TMD patients without fibromyalgia.

Conclusions: This study shows that some of the methods used to assess pain sensitivity do not work as researchers expect. However, the problems may be obscured when averaging responses across all participants in a group. Nevertheless, since TMD patients had more lingering painful aftersensations when the heated pad was removed, the researchers were able to support the concept that TMD patients, both those with and without fibromyalgia, have some form of disturbance of central nervous system-managed pain processing mechanisms.

TMJ Disorders

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