Temporomandibular Joint Disorders

Definition

Temporomandibular joint (TMJ) disorder, also known as TMD, is the name given to a group of symptoms that cause pain in the facial muscles and dysfunction in the head, face, and jaw. TMD often has psychological as well as physical causes.

Description

TMD results from pressure on the facial nerves due to muscle tension, injury, or bone abnormalities. Some 70% of adults exhibit at least one sign of TMD, but only 5% seek treatment. Most sufferers are women between ages 20 and 50.

The TMJ connects the temporal bone with the condyle of the mandible anterior to the ear on each side of the skull. The jaw pivots on ligaments, tendons, and muscles to allow motion downward and laterally as well as forward. Anything that causes a change in shape or functioning of the TMJ can cause pain and other symptoms.

Causes and symptoms

Causes

TMD has varied causes:

Bruxism, or unconscious clenching or grinding of the teeth, is the most common cause of TMD. Bruxism occurs during periods of stress or during sleep. It results in muscle tension and soreness around the jaw joint and in the facial muscles.
Misalignment of the teeth or displacement of the TMJ disc may contribute to TMD.
Injury to the jaw or side of the head, either from a direct blow or from repeated and prolonged opening and closing (as in gum chewing) can result in a dislocation of the TMJ and subsequent TMD problems.
Arthritis in different forms can lead to TMD. Traumatic arthritis from an injury, osteoarthritis, and rheumatoid arthritis are all possible causes.
Hypermobility, a condition in which the ligaments of the TMJ are too loose, may allow the mandible to slip out of position and create TMD.
Poor posture is another potential cause of TMD. When an individual carries his or her head too far forward and strains the neck muscles, TMD can result. In one research study in Texas, patients who were given posture training along with traditional treatment had greater improvement than those without posture training.
Birth abnormalities are the least frequent cause of TMD, but can occur. In some cases, the condyle of the mandible is too large or too small.

Symptoms

The symptoms of TMD depend in part on its cause. They include orofacial pain, restricted jaw function, and clicking or stiffness in the joints. Patients may also suffer from headaches, ear, neck, and shoulder pain, or tinnitus. A classic symptom is pain in front of the ear that spreads to the ear, mandible, cheek, and temple. Pain may be worse in the morning, and may be cyclical. Patients may also report noise in the joint during chewing, and limited mouth opening.

Diagnosis

Physical examination and patient history

TMD is most frequently diagnosed in the dental office based on physical examination. As the patient opens, closes, and moves the jaw laterally, palpation (physical examination by feeling with the hands) can detect joint popping and clicking, or a stethoscope may be placed in front of the ear to listen to the jaw movements. Jaw and facial muscles are checked for tenderness, and the patient's bite is checked for misalignment.

A careful patient history looks for such clues as recent injury or recent dental work. The patient should be asked about the duration and severity of jaw and face pain. Any history of insomnia, stress, anxiety, depression, chronic pain, or fibromyalgia should be documented.

Imaging studies

Imaging studies are not usually necessary to diagnose TMD. In most cases, x rays and magnetic resonance imaging (MRI) scans of the temporomandibular joint are normal. If the dentist suspects the patient has malpositioning of the TMJ disc, he or she can use arthrography to make the diagnosis. Arthrography can be used to evaluate the movement of the jaw and disc as well as their size and shape, and to evaluate the effectiveness of treatment.

Treatment

In 80% of TMD sufferers, symptoms improve in six months without treatment. When treatment is necessary, various modalities are used.

Phase I treatment

Phase I treatment is conservative and noninvasive, with no irreversible changes. Its purpose is to eliminate muscle spasms, swelling, and pain. Initially, a dentist may prescribe moist heat, aspirin, or a nonsteroidal anti-inflammatory drug, with a soft diet to alleviate symptoms.

Patients who have difficulty with bruxism are usually treated with splints. A plastic splint called a nightguard or mouthguard is constructed and worn at night. The splint can break the cycle of bruxing and allow sore muscles to relax. Splints can also be used to treat malpositioning by holding the mandible forward and keeping the disc in place until the ligaments tighten. The splint is adjusted over a period of two to four months.

Muscle relaxants can be prescribed if symptoms are related to muscle tension or fibromyalgia. If the TMD is related to rheumatoid arthritis, it may be treated with corticosteroids, methotrexate (MTX, Rheumatrex), or gold sodium (Myochrysine).

TMD can also be treated with ultrasound, electromyographic biofeedback, stretching exercises, transcutaneous electrical nerve stimulation, stress management techniques, friction massage, or posture training.

A patient who is suffering emotional or psychological problems that contribute to his or her TMD must address those problems before expecting relief of TMD symptoms.

Phase II treatment

By definition of the American Dental Association, Phase II treatment is non-reversible, invasive therapy. Its purpose is to definitively correct any discrepancies in the TMJ. Modalities include adjustment of the occlusion, orthodontics, reconstruction of the teeth, surgery, or a combination of these treatments.

In the 1980s, synthetic implants were used to replace the TMJ disc, but the implants proved to be too fragile to withstand jaw pressure. By 1999, all implants were taken off the market by the FDA. A new implant design was approved by the FDA in 2000.

Any patient considering Phase II treatment should be advised to get a second and possibly third opinion, and to proceed cautiously.

Prognosis

The prognosis for recovery from TMD is excellent for almost all patients. Most do not need any form of long-term treatment. In the case of patients with TMD associated with arthritis or fibromyalgia, the progression of the condition determines whether TMD can be eliminated.

Health care team roles

Every member of the dental team should be alert for TMD symptoms in patients, though only the dentist can prescribe treatment. A dental hygienist or assistant can use a skull or charts to help the patient understand the function and action of the TMJ. Additionally, dental auxiliaries can educate the patient about correct posture and modifying behavior such as gum chewing and fingernail biting.

If the dentist determines a splint is necessary, the hygienist or assistant can take impressions of the teeth and prepare plaster casts from the impressions. A dental laboratory technician then constructs the splint, and the dentist places it, checking to ensure an exact fit.

Prevention

To prevent TMD from developing, suggestions to patients can include:

Avoid overuse of the jaw. Gum chewing is the major culprit, along with fingernail biting.
Try not to grind the teeth. Follow the "lips together, teeth apart" rule. Upper and lower teeth should meet only for chewing. Make a conscious effort to keep the masseter (cheek) muscles relaxed.
Sleep on the back. Sleeping on either side can put pressure on the TMJ.
Manage stress. Relaxation exercises and biofeedback can help.
Use correct posture. Carrying the head in a forward position has been shown to affect TMD. Also, correct bad ergonomic habits such as holding a telephone receiver between the ear and shoulder.

KEY TERMS

Arthrography—A testing technique in which a special dye is injected into the joint, which is then x rayed.

Bruxism—Habitual clenching and grinding of the teeth, especially during sleep.

Condyle—An articular prominence of a bone.

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.

Fibromyalgia—A complex, chronic condition which causes widespread pain and fatigue, as well as a variety of other symptoms.

Malocclusion—The misalignment of opposing teeth in the upper and lower jaws.

Mandible—The lower jaw.

Orofacial—Pertaining to the mouth and face.

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 right and left sides of the skull above the ears.

Tinnitus—A sensation of ringing or roaring in the ears that can only be heard by the individual affected.

Transcutaneous electrical nerve stimulation—A method for relieving the muscle pain of TMD by stimulating nerve endings that do not transmit pain. It is thought that this stimulation blocks impulses from nerve endings that do transmit pain.