TMJ and TMD
The TMJ is a synovial hinge and planar joint. This means only that the joint is surrounded by a capsule of muscle which is lined with a fluid producing membrane called the synovium. It is this fluid which feeds the internal structures which do not have blood vessels or nerves. These internal structures include the cartilage, ligaments and connective tissues. This joint is located just in front of your ear hole. When you first begin to open, the "ball-like" part of the lower jaw simply rotates inside its own cartilage. This represents the first 19-23 millimeters of mouth opening. As the jaw opening continues, the ball and cartilage together slide down and forward, riding on a part of the skull called the eminence until the jaw is fully open. This opening, or joint flexion, is limited by a ligament connected to the ball similar to any other joint in the body. The major difference between this joint and all the others occurs when we close our mouth and extend the joint back. The difference is that the TMJ does not have a ligament to limit this movement as do all the other joints. Instead, the only limit to this closing movement occurs when the teeth come together. This, we believe to be the pivotal point in understanding the TMJ. For the health of this joint the teeth function as a ligament functions in other joints. If some teeth stop the closing movement, limiting the joint movement to a normal range of motion, this joint works well. If nothing comes together soon enough, the joint movement will continue beyond its intended range of motion, (hyperextend), and will incur joint dysfunction and damage of some kind. The confusion exists due to the fact that you must see a dentist because the teeth are involved; however, the dentist needs to treat a ligament problem in a joint. As the ball continues into the back of the joint, it places pressure on the tissue in that area that contains blood vessels and nerves. These tissues produce both the joint pain and inflammation of the TMD.
Diagnosis
No effective treatment for any issue can occur without good diagnosis first. In the world of TMJ, this requires MRI evaluation. I, and a separate clinician participated in an early project with the use of MRI and found that we both were wrong 23% of the time when compared to the MRI findings. Since then, three other studies have been done with similar results. The most recent found the error rate to be 34%. This comparison included all other forms of diagnosis, including C. T. scans, other x-rays, joint vibration analysis, Doppler, etc. Basically, a patient must realize that if no MRI was done, no diagnosis has been made. Prior to the advent of MRI, labeled arthrograms were effective but were invasive, unpleasant if not painful, and it could take weeks for a full recovery. For these reasons they were not used routinely and have been abandoned since MRI became available.
