The science of pain

The science of pain

Large-scale study sheds light on jaw disorder TMJ

By Karen Rhodenizer

Roger Fillingim (with Marissa Burns) leads UF’s site for the Orofacial Pain Prospective Evaluation and Risk Assessment study./Photo by Maria Belen Farias

A large clinical study of painful jaw problems commonly known as TMD disorders has revealed a wide range of findings, including how women apparently grow more vulnerable to the condition as they age.

Writing in the November issue of the Journal of Pain, a multi-institutional team of researchers, including scientists with the UF College of Dentistry, revealed the results of the Orofacial Pain Prospective Evaluation and Risk Assessment study, or OPPERA.

One of the largest clinical investigations into the causes of what are technically known as temporomandibular joint disorders, or TMD, researchers hope the discoveries may lead to new methods of diagnosing and treating facial pain conditions, and predicting who will be susceptible to them.

“A major benefit of the OPPERA study is the comprehensive evaluation of demographic, clinical, biological, sensory and psychosocial factors that may contribute to increased risk of TMD,” said Roger Fillingim, Ph.D., a professor of community dentistry and behavioral science at the UF College of Dentistry and the principal investigator for the UF OPPERA site.

Temporomandibular joint disorders, sometimes referred to as TMJ, produce pain that radiates from the jaw and surrounding muscles, restricting jaw movement and causing considerable suffering. Although the disorders vary in duration and severity, for some people the pain becomes a permanent feature of their lives. Estimates suggest more than 10 million people are affected by TMD disorders, according to the National Institute of Dental and Craniofacial Research.

Researchers followed 3,200 initially pain-free individuals for three to five years, comparing them with 185 people who had long-standing, chronic TMD.

They found chronic TMD becomes more frequent with increasing age in women but not in men. Early studies indicated women’s greatest risk occurred during early childbearing years and decreased thereafter.

In addition, a wide range of biological and psychological factors appear to contribute to the condition. People with TMD were much more sensitive to mildly painful sensations than pain-free individuals. They were more aware of body sensations and experienced greater heart rate increases during mild physical and psychological stress, too.

Researchers believe the findings provide evidence that chronic TMD is at least partially linked to a person’s perception of and ability to suppress pain, which is determined by the body’s physiological regulatory systems.

Researchers also identified new and important genetic factors that appear to be linked to chronic TMD. Several genes, including some known to influence stress response, psychological well-being and inflammation, were identified and may result in new targets for treatment.

The longitudinal study builds on earlier work by members of the multi-university research team, which designed a broad conceptual model to determine the condition’s causes.

“The OPPERA conceptual model proposes that measures of pain sensitivity and psychosocial functioning, both of which are influenced by life experiences as well as genetics, are related to future development of TMD,” Fillingim said. “While the OPPERA conceptual model was developed initially to explain risk for developing TMD, it can be more broadly applied and may help explain the reasons some people develop many different chronic pain conditions.”

The National Institute of Dental and Craniofacial Research-funded study was conducted across four study sites, including UF, UNC-Chapel Hill, UF, the University of Maryland at Baltimore, the University of Buffalo and Battelle Memorial Institute.