Risk Factors for Chronic TMJ and Muscle Disorders



Scientists affiliated with a large, 7-year study, entitled Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA), supported by the National Institute of Dental and Craniofacial Research (NIDCR), have published the preliminary results of the most comprehensive and systematic analysis to date of risk factors associated with chronic temporomandibular joint and muscle disorders (TMJD). These findings are published in a special issue of the Journal of Pain and include:
• In women, the risk for chronic TMJD increases between the ages of 18 and 44 years, 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 to 44 years), age was unrelated to TMJD incidence.
• Chronic TMJD incidence does not correlate with low socioeconomic status. This finding is in stark contrast to trends seen in other chronic pain conditions. 
• 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.
• 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 or 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 Dr. Martha Somerman, the director of NIDCR. “[It] has a lot more data in the pipeline. The next few years will be extremely interesting and should greatly improve the diagnosis of TMJD.”

(source: NIDCR, November 10, 2011)