For many years the TMJA has asked agencies of the National Institutes of Health (NIH) to convene a meeting to assess what we know about the TM joint and to determine gaps in our knowledge. On May 3, 2013, the NIH held a scientific round table of experts to do just that. The following is a summary of the meeting.
Some things we do know about the temporomandibular joint. It’s the most complex joint in the body enabling movement in 3 dimensions: forward and back, side to side, and up and down. Also, it’s paired. Unlike other joints in the body your two TMJs work as a team, coordinating their motions. Finally, the composition of the soft tissue of the joint differs from soft tissue of other joints. But otherwise the joint remains mysterious, an orphan in terms of study—excluded by scientists who investigate other joints in the body, and not much adopted by dental researchers either. The TMJ Association has for years asked the National Institutes of Health (NIH) to address this problem, with the result that a workshop to explore what is and what is not known about the joint was convened on May 3. Three agencies of the NIH—the National Institute of Dental and Craniofacial Research NIDCR), the National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the National Institute of Biomedical Imaging and Bioengineering sponsored the workshop. They invited thirteen experts, most from bioengineering and orthopedic research, to address the structure and function of the bone, muscle, cartilage and other components of the joint, and the various tools available to measure joint properties. The intent of the meeting was to have selected attendees present data followed by open-ended discussions about what research needs to be done, formulated as recommendations.
What we learned. There were lots of interesting observations—and just as many provocative questions. An initial presentation summarized that TM disorders are common, more prevalent in women, and often resolve by themselves. Persistent cases are predominantly myofascial in type and it was suggested that this type might also be associated with the co-morbid pain conditions many TMD patients experience. It’s not clear why TMD cases fall off after age 50—a time when arthritic problems in other joints are likely to increase. What was clear was that at this time there are no effective TMD treatments. A video showed the position of the cartilaginous disc atop the upper end of the mandible (the condyle) in normal movement and under various forms of displacement; the latter considered a pathological change in categorizing forms of TMD. Yet some people have displaced discs over their lifetimes and they never experience pain. Much of the discussion stressed the dynamics of the joint: how it is affected by the amount of loading put on it, a factor which in turn affects the quality of the bone, muscles, ligaments, and blood supply of the joint. Alternatively, limited use of the joint because of disease and pain may further exacerbate problems by weakening bone and muscles, the continued invasion of inflammatory markers, and so on, in a vicious cycle.
It was not clear which comes first in TM disease: cartilage degeneration, followed by bone loss, or vice versa. Another issue was the effect of periodontal disease and the serious consequences it might have on jaw bone quality. But under the right conditions bone and cartilage can regenerate and much talk was directed at the class of molecules and cascade of events needed to encourage building of healthy new tissue and how such processes can be mediated using bioengineering techniques. The group decried the lack of good models of human jaw development and disease as well as the need for greater refinements in instruments to measure jaw mechanics and more detailed biomedical imaging.
However complex the dynamics of the TM joint may be, what was heartening was the dynamic quality of the meeting itself. The invited researchers engaged in lively discussions raising questions they had not considered before and discussing ideas with investigators outside their chosen fields. That point was made by Dr. Lawrence Tabak, Principal Deputy Director of the NIH and former NIDCR Director, who joined the gathering late in the day to compliment the organizers. He emphasized that if progress is to be made in understanding the TM joint in health and disease it will depend up on the cross-collaboration among researchers in the dental, musculoskeletal and bioengineering worlds. The outcome of the meeting will be a set of research recommendations which will be circulated widely and which we will publish on our website.
Joan Wilentz, The TMJ Association