Temporomandibular joint disorder (TMJ) is the name given to a group of symptoms that cause pain in the head, face, and jaw. The symptoms include headaches, soreness in the chewing muscles, and clicking or stiffness of the joints. They often have psychological as well as physical causes.
Description
TMJ disorder, which is also sometimes called TMJ syndrome, results from pressure on the facial nerves due to muscle tension or abnormalities of the bones in the area of the hinge joint between the lower jaw and the temporal bone. This hinge joint is called the temporomandibular joint. There are two temporomandibular joints, one on each side of the skull just in front of the ear. The name of the joint comes from the two bones that make it up. The temporal bone is the name of the section of the skull bones where the jaw bone (the mandible) is connected. The jaw bone is held in place by a combination of ligaments, tendons, and muscles. The temporomandibular joint also contains a piece of cartilage called a disc, which keeps the temporal bone and the jaw bone from rubbing against each other. The jaw pivots at the joint area in front of the ear. The pivoting motion of the jaw is complicated because it can move downward and from side to side as well as forward. Anything that causes a change in shape or functioning of the temporomandibular joint will cause pain and other symptoms.
Causes
TMJ syndrome has several possible physical causes:
Muscle tension. Muscle tightness in the temporomandibular joint usually results from overuse of muscles. This overuse in turn is often associated with psychological stress and clenching or grinding of the teeth (bruxism).
Injury. A direct blow to the jaw or the side of the head can result in bone fracture, soft tissue bruising, or a dislocation of the temporomandibular joint itself.
Internal derangement. Internal derangement is a condition in which the cartilage disk lies in front of its proper position. In most cases of internal derangement, the disc moves in and out of its correct location, making a clicking or popping noise as it moves. In a few cases, the disc is permanently out of position, and the patient's range of motion in the jaw is limited.
Hypermobility. Hypermobility is a condition in which the ligaments that hold the jaw in place are too loose and the jaw tends to slip out of its socket.
Birth abnormalities. These are the least frequent cause of TMJ but do occur in a minority of patients. In some cases, the top of the jawbone is too small; in others, the top of the jawbone outgrows the lower part.
Symptoms
The symptoms of TMJ depend in part on its cause. The most common symptoms are facial pain in front of the ears; headaches; sore jaw muscles; a clicking sound when chewing; a grating sensation when opening and closing the mouth; and temporary locking of the jaw. Some patients also report a sensation of buzzing or ringing in the ears. Usually, the temporomandibular joint itself is not painful. Most cases of TMJ are seen in women between 20-50 years of age.
Dental examination and patient history
TMJ disorders are most frequently diagnosed by dentists. The dentist can often diagnose TMJ based on physical examination of the patient's face and jaw. The examination might include pressing on (palpating) the jaw muscles for soreness or asking the patient to open and close the jaw in order to check for misalignment of the teeth in the upper and lower jaw. This condition is called malocclusion. The dentist might also gently move the patient's jaw in order to check for loose ligaments.
Imaging studies
Imaging studies are not usually necessary to diagnose TMJ. In most cases, x rays and MRI scans of the temporomandibular joint will be normal. Consequently, these two tests are not commonly used to diagnose TMJ. If the dentist suspects that the patient has internal derangement of the disc, he or she can use a technique called arthrography to make the diagnosis. In an arthrogram, a special dye is injected into the joint, which is then x-rayed. Arthrography can be used to evaluate the movement of the jaw and the disc as well as size and shape, and to evaluate the effectiveness of treatment for TMJ.
Treatment
In many cases, the cause of pain in the TMJ area is temporary and disappears without treatment. About 80% of patients with TMJ will improve in six months without medications or physical treatments.
Medications
Patients with TMJ can be given muscle relaxants if their symptoms are related to muscle tension. Some patients may be given aspirin or nonsteroidal antiinflammatory drugs (NSAIDs) for minor discomfort. If the TMJ is related to rheumatoid arthritis, it may be treated with corticosteroids, methotrexate (MTX, Rheumatrex) or gold sodium (Myochrysine).
Physical therapy and mechanical devices
Patients who have difficulty with bruxism are usually treated with splints. A plastic splint called a nightguard is given to the patient to place over the teeth before going to bed. Splints can also be used to treat some cases of internal derangement by holding the jaw forward and keeping the disc in place until the ligaments tighten. The splint is adjusted over a period of two to four months.
TMJ can also be treated with ultrasound, electromyographic biofeedback, stretching exercises, transcutaneous electrical nerve stimulation, stress management techniques, or friction massage.
Surgery
Surgery is ordinarily used only to treat TMJ caused by birthdeformities or certain forms of internal derangement caused by misshapen discs.
Prognosis
The prognosis for recovery from TMJ is excellent for almost all patients. Most patients do not need any form of long-term treatment. Surgical procedures to treat TMJ are quite successful. In the case of patients with TMJ caused by arthritis or infectious diseases, the progression of the arthritis or the success of eliminating infectious agents determines whether TMJ can be eliminated.
BOOKS
"Disorders of the Temporomandibular Joint." In Merck Manual of Medical Information: Home Edition, ed. Robert Berkow, et al. Whitehouse Station, NJ: Merck Research Laboratories, 1997.
Murphy Jr., William A., and Phoebe A. Kaplan, "Temporomandibular Joint." In Diagnosis of Bone and Joint Disorders, ed. Donald Resnick. Philadelphia: W. B. Saunders Co., 1995.
John T. Lohr, PhD
KEY TERMS
Arthrography—An imaging technique that is sometimes used to evaluate TMJ associated with internal derangement.
Electromyographic biofeedback—A method for relieving jaw tightness by monitoring the patient's attempts to relax the muscle while the patient watches a gauge. The patient gradually learns to control the degree of muscle relaxation.
Internal derangement—A condition in which the cartilage disc in the temporomandibular joint lies in front of its proper position.
Malocclusion—The misalignment of opposing teeth in the upper and lower jaws.
Mandible—The medical name for the lower jaw.
Osteoarthritis—A type of arthritis marked by chronic degeneration of the cartilage of the joints, leading to pain and sometimes loss of function.
Rheumatoid arthritis—A chronic autoimmune disorder marked by inflammation and deformity of the affected joints.
Temporal bones—The compound bones that form the left and right sides of the skull.
Transcutaneous electrical nerve stimulation—A method for relieving the muscle pain of TMJ by stimulating nerve endings that do not transmit pain. It is thought that this stimulation blocks impulses from nerve endings that do transmit pain.
