Temperomandibular joint disorder is a stress-related condition characterized by clicking in the jaw and pain in the face or neck and is often associated with neckaches and headaches. The jaw may click out of place (perhaps with a slipped disc) or even lock in a closed position. The condition is often painful and normal jaw movements slow to restore. A traumatic physical event, such as yawning very widely, coupled with an uneven bite, or a muscle spasm may be the cause. To a lesser degree many people excessively clench their teeth by contracting their jaw muscles in response to stress or grind their teeth at night. More rarely, the jaw may be damaged by arthritis, which is associated with "crunching" noises.
TMD refers to a collection of conditions in and around the temporomandibular joint, which connects the mandible, or lower jaw, to the temporal bone of the skull. TMD's pain and dysfunction often disappear after several months with little or no treatment, leaving patients relieved and practitioners puzzled. Whilst they are suffering however, people tend to move from dentists and oral surgeons to rheumatologists, ear, nose and throat specialists and other physicians -- all of whom disagree about which TMD problems should be treated, and when and how to do so.
In the '70s and '80s, even people in the early stages of TMD typically were treated aggressively on the theory that it was necessary to make their anatomy "normal" by repositioning their teeth or jaws. But 80 percent of repositioned jaw discs slip back again within two years. Many experts now consider that the vast majority of patients with temporomandibular disorders should initially receive noninvasive, reversible therapies; perhaps only 1 to 2 percent of TMD patients, typically people who need total joint replacement because of rheumatoid arthritis or bad implants, can benefit from surgery.
Perhaps half the population live with some symptoms of temperomandibular joint dysfunction. In the USA it is estimated that 12 million have aching jaws.
Women in their reproductive years are twice as likely as men to get TMD, probably because the production of oestrogen has the effect of loosening their ligaments.
It is estimated that an improper bite accounts for at most 10 to 20 percent of TMD cases.