Temporomandibular Disorders (TMDs)

Temporomandibular myofascial pain syndrome is the most common disorder affecting the temporomandibular region. Muscle pain and tightness around the jaw and limited mouth opening occur, as well as headache and pain in other areas of the head and neck. Pain is caused mainly by muscle fatigue or overuse, sometimes resulting from clenching or grinding the teeth while awake or asleep due to psychologic or sleep-related stress. Clenching and grinding while asleep exert far more force than clenching and grinding while awake. Pain can also be brought on by injury to the head or neck, sleep disorders, problems of misalignment of the upper and lower sets of teeth, or even toothache. The TMJ can be normal. Temporomandibular myofascial pain syndrome is more common among women and typically affects women in their early 20s and women who are nearing or going through menopause.

The Temporomandibular Joint

In the most common form of internal TMJ derangement, the disk inside the joint lies in front of (anterior to) its normal position. The disk can be moved out of place when the ligaments that hold it in place become elongated or, often, stretched due to injury to the joint (sprained ligament).

Internal TMJ derangement can occur with or without reduction. Reduction means the parts of a joint have returned to their normal positions. Disk displacement with reduction is more common than displacement without reduction and occurs in about one third of the adult population. In derangement with reduction, the disk lies in front of its normal position only when the mouth is closed. As the mouth opens and the jaw slides forward, the disk slips back into its normal position, often making a popping or clicking sound. As the mouth closes, the disk slips forward again. In internal TMJ derangement without reduction, the disk never slips back into its normal position, and the degree to which the mouth can be opened is limited. TMJ derangement can cause inflammation around the joint (capsulitis). Internal TMJ derangements may or may not be painful.

Arthritis in a temporomandibular joint may result from osteoarthritis, rheumatoid arthritis, infectious arthritis, or injury, particularly injury that causes bleeding into the joint. Such injuries are fairly common among children who are struck directly on the chin or on the side of the chin.

Osteoarthritis, a type of arthritis in which the cartilage of the body's joints degenerates, is most common among people over age 50. Osteoarthritis of the TMJ may occur when the fibrocartilage disk inside the joint is displaced or has developed holes, causing the bone of the joint to change shape as part of degenerative changes.

Rheumatoid arthritis, a disease in which the body attacks its own cells (an autoimmune disease) causing inflammation, affects the temporomandibular joint in about 17% of people with this type of arthritis. The temporomandibular joint is usually among the last joints to be affected by rheumatoid arthritis.

Infectious arthritis is caused by an infection that has spread from an adjoining area of the head or neck or that has been carried by the bloodstream to the joint from another part of the body.

Traumatic arthritis, which is arthritis caused by an injury (such as when the jaw is stretched widely during a difficult tooth extraction), is rare.

Ankylosis is loss of joint movement resulting from a fibrosing (scarring) or fusion of bones within the joint or from calcification (the deposit of calcium into body tissues) of the ligaments around it. Ankylosis most often results from an injury or an infection, but it may be apparent at birth or a result of rheumatoid arthritis.

Hypermobility (looseness of the jaw) results when the ligaments that hold the joint together become excessively elongated, like being double-jointed. In hypermobility, dislocation is usually caused by the shape of the joints, ligament looseness (laxity), and muscle tension. It may be caused by trying to open the mouth too wide or by being struck on the jaw.

People with temporomandibular myofascial pain syndrome (previously known as temporomandibular joint [TMJ] syndrome or TMJ dysfunction) may feel pain, fatigue, and tightness on the sides of the face when awakening or after stressful periods during the day. Clenching and grinding of the teeth while asleep and sleep-disordered breathing, such as obstructive sleep apnea, may cause a person to awaken with a headache, which may slowly diminish over the day. However, some people have symptoms while awake, including a headache, if they continue to clench and grind their teeth while awake. As the jaw opens, it may move slightly (deviate) to one side or the other and may not open all the way. The chewing muscles are typically painful and tender to the touch. Small spots or knots in the muscles (called trigger points) are tender and when pressed can cause referred pain in other locations in the head and neck.

Internal joint derangement related to anterior disk displacement with reduction usually causes a clicking or popping sound in the joint when the mouth opens wide or the jaw shifts from side to side. Other people are sometimes able to hear these sounds. In many people, these joint sounds are the only symptoms. However, some people also have pain, particularly when chewing foods with a tough consistency. In a small percentage of people, these sounds progress to locking of the joints.

Internal joint derangement related to anterior disk displacement without reduction does not cause a sound but makes it difficult for people to open their mouth wide. It usually causes pain and a feeling that the joint is out of place. Typically, this type of joint derangement starts suddenly in people whose joint previously clicked all the time (anterior disk displacement with reduction). Sometimes people discover they are not able to fully open their jaw when they wake up. After 6 to 12 months, the pain may decrease, and the limitation on how much the mouth can be opened may resolve.

With osteoarthritis, because it occurs mainly when the disk is out of place or has developed holes, the person feels and often hears a grating sensation in the temporomandibular joints when opening and closing the mouth. Stiffness, mild pain, or a combination may occur. When osteoarthritis is severe, the top of the jawbone flattens out, and the person cannot open the mouth wide. The jaw may also shift toward the affected side, and the person may be unable to move it back. The person may notice a change in how the upper and lower teeth meet on the unaffected side.

Rheumatoid arthritis causes pain, swelling in the temporomandibular joint, and limited jaw movement. It usually affects both temporomandibular joints about equally, which is rarely the case in other types of TMDs. When rheumatoid arthritis is severe, especially in children, the top of the jawbone may degenerate and shorten, causing deformities of the face. This damage can lead to rapid misalignment of many or all of the upper and lower teeth. Though rare, if the damage is severe, the bones of the joint may eventually fuse together (ankylosis).

In infectious arthritis, the area over and around the temporomandibular joint is inflamed, and jaw movement is limited and painful.

Traumatic arthritis causes pain and tenderness in the temporomandibular joint, and limitation of jaw movement.

Typically, fusion of the ligaments and bone around the joint (extra-articular ankylosis) is not painful, but the mouth can open only about 1 inch (about 2½ centimeters) or less. Fusion of bones within the joint (intra-articular ankylosis) causes pain and more severely limits jaw movement.

In a person with hypermobility, the jaw may slip forward completely out of its socket (dislocate), causing pain and an inability to close the mouth. Dislocation may occur suddenly and repeatedly.

Oral appliance

An oral appliance often is the main treatment for jaw muscle pain and tightness. For people who realize that they clench or grind their teeth, oral appliance therapy can help them break the habit. A thin plastic oral appliance is made by a dentist to fit over either the upper or the lower set of teeth and is adjusted to give the person an even bite. The oral appliance, usually worn while sleeping (a nightguard), often reduces grinding and clenching, allowing the jaw muscles to rest and recover. For pain while awake, an oral appliance allows the jaw muscles to remain relaxed and the bite to be stable, thereby reducing discomfort. The oral appliance can also prevent damage to teeth that are under exceptional stress from the grinding and clenching. Oral appliances are used while awake only until symptoms subside, usually less than 8 weeks. Longer use may be warranted depending on the severity of symptoms.

Self-help measures

People should use self-help measures to relieve pain and restore normal function.

• Switching to a diet of softer foods, cutting food into smaller pieces, chewing slowly, and not opening the mouth as wide will decrease muscle tension and stress on the temporomandibular joints.

• Keeping the upper and lower teeth apart while awake will help break the habit of clenching or grinding the teeth, also decreasing muscle tension and stress on the temporomandibular joints.

• Developing some system to help remember to correct poor posture will help the jaw and neck/shoulder muscles recover.

• Following proper sleep behavior, including going to sleep at the same time in a quiet and comfortable environment, will decrease pain and allow the body to heal.

• Applying moist heat to fatigued muscles will also help.

Physical therapy

Physical therapy may also be prescribed. Physical therapy may involve ultrasound treatment, electromyographic biofeedback (in which the person learns to relax the muscles), spray and stretch exercises (in which the jaw is stretched open after the skin over the painful area has been sprayed with a skin refrigerant or numbed with ice). Transcutaneous electrical nerve stimulation (TENS—see sidebar Physical Therapy for Jaw Muscles) also may help. Stress management, sometimes along with electromyographic biofeedback, and counseling help some people.

Medications

obstructive sleep apnea, should ask their doctor before using any benzodiazepines or sedatives (including over-the-counter sleep aids) or muscle-relaxing drugs because these drugs can worsen that disorder.

Botulinum toxin injected into the muscle or anesthetics injected into muscular trigger points have been used to relieve muscle spasms and pain.

In some cases of chronic pain, antidepressant drugs may be useful.

Regardless of the type of treatment, most people experience significant relief within about 3 months. If the symptoms are not severe, many people recover without treatment.

In internal joint derangement with or without reduction, treatment is needed only if a person has jaw pain or trouble moving the jaw. People are often given NSAIDs for pain. If a person seeks treatment right after symptoms develop, a dentist or doctor may be able to manually move the disk back into its normal position.

If a person has had the disorder for fewer than 3 to 6 months, an oral anterior repositioning appliance may be used. The appliance holds the lower jaw forward, keeps the disk in position, and permits the supporting ligaments to tighten and become pain free. Over 2 to 4 months, the oral appliance is adjusted to allow the jaw to return back to its normal position, with the expectation that the disk will remain in place. However, the longer the disk is displaced, the less likely its repositioning will succeed.

A person with internal joint derangement with or without reduction should avoid opening the mouth wide—for instance, when yawning or biting into a thick sandwich—because injured joints are not as protected in these activities as they would be in a normal jaw. People with this disorder are advised to cut food into small pieces and to eat food that is easy to chew.

Sometimes the slipped disk becomes stuck in front of the temporomandibular joint (TMJ), preventing the jaw from opening fully. The disk must then be manually moved even further out of position to allow the joint to move fully. Passive jaw-motion devices, which stretch the jaw, have been used to slowly increase jaw motion. These devices are used several times a day. One such device is a threaded screw-type instrument that is placed between the front teeth and turned, much like a car jack, to gradually and gently push the disk forward, thereby creating a wider mouth opening. If such a device is not available, then a doctor may use a stack of tongue depressors placed between the front teeth, with an additional tongue depressor being added to the middle of the stack to increase mouth opening little by little.

If internal joint derangement cannot be treated by nonsurgical means, an oral and maxillofacial surgeon may need to do surgical procedures. However, the need for traditional surgery is rare since the introduction of procedures such as arthroscopy. All surgical procedures are used in combination with oral appliance therapy, self-help measures, and supervision by a dentist or doctor.

A person with osteoarthritis

Rheumatoid arthritis of the temporomandibular joint is treated with the medications used for rheumatoid arthritis of any joint. NSAIDs may be given for severe pain. Maintaining joint mobility and preventing fusion of the joint are particularly important. Usually, the best way to accomplish these goals is by exercising the jaw under a physical therapist's direction. To relieve symptoms, particularly muscle tightness, the person wears an oral appliance during sleep. If joint fusion prevents all movement of the jaw, the person may need surgery and, in rare cases, an artificial joint to restore jaw mobility.

Infectious arthritis is treated with antibiotics, proper hydration, pain control, and restriction of movement. Penicillin is usually the antibiotic used initially, until test results determine the type of bacteria present and thus the best antibiotic to use. Pus in the joint, if present, may be removed with a needle. Once the infection is controlled, people do jaw-opening exercises to help prevent scarring and limitation of motion.

Traumatic arthritis is treated with NSAIDs and corticosteroids (drugs that reduce inflammation and ease its symptoms such as swelling, redness, and pain), application of heat, a soft diet, and restriction of jaw movement.

Occasionally, jaw-opening exercises can help, but people with bone fusion usually need surgery to restore jaw movement, and exercises are then needed for months to years to maintain the surgical correction.

Prevention and treatment of dislocation resulting from hypermobility are the same as those for other causes of a dislocated jaw. When dislocation occurs, help is sometimes needed to snap the jaw back into position. Many people who experience repeated dislocations, however, learn how to maneuver the joint back into place themselves by consciously relaxing the muscles and lightly shifting the lower jaw until it pops back into place. To prevent recurrent dislocations, doctors may inject a substance into the joint (for example, blood) that causes scarring and thereby reduces mobility. Surgery to reshape the bone or tighten the ligaments around the temporomandibular joint is sometimes necessary to prevent recurrent dislocations.