Study evaluates risk factors for chronic TMJD

Thousands of Americans this year will be diagnosed with a common disorder of the jaw area called temporomandibular joint and muscle disorders (TMJD, formerly called TMJ). Because of the inherent biological complexity of TMJD, their healthcare providers will have no way to determine whether their patients will get better in time or battle chronic disease.

But research help is on the way. Scientists affiliated with a large, seven-year study supported by the National Institute of Dental and Craniofacial Research (NIDCR), part of the National Institutes of Health, have published the preliminary results of the most comprehensive and systematic analysis to date of risk factors associated with chronic TMJD. The findings are found in a special issue of the Journal of Pain, which now is available online to subscribers.

These initial results from the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) study provide a voluminous body of high-quality data that confirms many previous discoveries and adds several new possibilities for risk. These include:

In women, the risk for chronic TMJD increases between the ages of 18 and 44, the age range evaluated in the study. Previous studies have suggested that the risk was greatest during a woman's early childbearing years and decreased thereafter. In young men (ages 18-44), age was unrelated to TMJD incidence.

Chronic TMJD incidence does not correlate with low socio-economic status. This finding is in stark contrast to trends seen in other chronic pain conditions. Socio-economic status, for instance, has been shown to have a profound effect on musculoskeletal pain, sciatica, ulcer, and neuropathic pain.

Chronic TMJD seems to be associated with alterations in some parts of the nervous system that control pain perception. Researchers found that TMJD patients, when compared to healthy study volunteers, were much more sensitive to a variety of stimuli that evoke mildly painful sensations. They also show elevated heart rate responses at rest and during mild physical and psychological stress.

Genetic variability contributes to chronic TMJD. Researchers found that chronic TMJD patients had alterations in several genes, including some known to influence stress response, psychological well-being, and inflammation. These findings may help to explain the origins of TMJD and provide new targets for drugs to treat chronic pain.

Several clinical findings also were reported. TMJD patients frequently experienced many more chronic pain conditions, such as lower back pain, headaches, and fibromyalgia. Evidence of abnormal jaw function associated with teeth grinding and clenching was also observed. Future investigations will attempt to unravel whether grinding and clenching is a cause of consequence of the condition.

"These initial results from the OPPERA Study mark an important preliminary first step in providing a clearer, more definitive accounting of the risk factors associated with TMJD and related conditions," said Martha Somerman, D.D.S, Ph.D., director of NIDCR. "The OPPERA Study has a lot more data in the pipeline. The next few years will be extremely interesting and should greatly improve the diagnosis of TMJD."