Temporomandibular joint disorders
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. 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. Thename of the joint comes from the two bones that make it up. The temporal boneis the name of the section of the skull bones where the jaw bone (the mandible) is connected. 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. Anything that causes a change in shape or functioning of the temporomandibularjoint will cause pain and other symptoms.
TMJ syndrome has several possible physical causes:
- Muscle tension. Muscle tightness in the temporomandibular joint usually results from overuse ofmuscles. 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.
- Arthritis. Both osteoarthritis and rheumatoid arthritis can cause TMJ.
- Internal derangement. Internal derangement is a condition in which the cartilage disk lies in front of its proper position. In most cases of internalderangement, 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.
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 calledmalocclusion. The dentist might also gently move the patient's jaw in order to check for loose ligaments. 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 theeffectiveness of treatment for TMJ.
In many cases, the cause of pain in the TMJ area is temporary and disappearswithout treatment. About 80% of patients with TMJ will improve in six monthswithout medications or physical treatments. Patients with TMJ can be given muscle relaxants if their symptoms are related to muscle tension. Some patientsmay be given aspirin or nonsteriodal anti-inflammatory 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).
Patients who have difficulty with bruxism are usually treated with splints. Aplastic splint called a nightguard is given to the patient to place over theteeth 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 placeuntil 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, stress management techniques, or massage. Surgery is ordinarily used only to treat TMJ caused by birth deformities or certain forms of internal derangement caused by misshapen discs.
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 byarthritis or infectious diseases, the progression of the arthritis or the success of eliminating infectious agents determines whether TMJ can be eliminated.