Disorders of The Temporomandibular Joint
The temporomandibular joints are the two places - one on each side of the face, just in front of the ears - where the temporal bone of the skull connects to the lower jaw (mandible). Ligaments, tendons, and muscles support the joints and are responsible for jaw movement.
The Temporomandibular Joint is The Most Complicated Joint in The Body:
It opens and closes like a hinge and slides forward, backward, and from side to side. During chewing, it sustains an enormous amount of pressure. The temporomandibular joint contains a piece of specialised cartilage called a disk that keeps the lower jawbone and skull from rubbing against each other.
Temporomandibular joint disorders, often called TMJ, include problems with the joints and the muscles surrounding them. Most often, the cause of temporomandibular joint disorder is a combination of muscle tension and anatomic problems within the joints. Sometimes, there’s a psychological component as well. These disorders are most common in women between ages 20 and 50.
Headaches, tenderness of the chewing muscles, and clicking or locking of the joints. Sometimes the pain seems to occur near the joint rather than in it. Temporomandibular joint disorder maybe the reason for recurring headaches that do not respond to usual medical treatment.
Dentists almost always diagnose temporomandibular joint disorder based simply on a person’s medical history and a physical examination. Part of the examination involves pushing on the side of the face or placing the little finger in the per-son’s ear and gently pressing forward while the person opens and closes the jaw. Also, the dentist gently palpates the muscles used for chewing to detect pain or tenderness and notes whether the jaw slides when the person bites.
Special X-ray techniques can help a dentist make the diagnosis. When a dentist suspects that the disk lies in front of its normal position (a condition called internal derangement), an X-ray in which dye is injected into the joint (an arthrogram) may be used. Though expensive, a computed tomography (CT) or magnetic resonance imaging (MRI) scan is used in rare instances to find out why a person is not responding to treatment. Laboratory tests are rarely useful. Dentists occasionally use electromyography, which analyzes muscle activity, to monitor treatment and less commonly to make a diagnosis.
Eighty per cent of people get better in six months without any treatment. From most to least common, temporomandibular joint disorders requiring treatment are muscle pain and tightness, internal derangement, arthritis, injury, reduced or excessive mobility of the joint, and developmental (birth) abnormalities.
Muscle Pain and Tightness
Muscle pain and tightness around the jaw come mainly from muscle overuse, often brought on by psychological stress that causes a person to clench or grind the teeth (bruxism). Most people can place the tips of their index, middle, and ring fingers held vertically in the space between the upper and lower front teeth without forcing. When a person has problems with the muscles around the temporomandibular joint, this space usually is smaller.
People with muscle pain usually have very little pain in the joint itself. Rather, they feel pain and tightness on the sides of the face upon awakening or after stressful periods during the day. This pain and tightness result from muscle spasms brought on by repeated muscle or tooth clenching and tooth grinding. Clenching and grinding while asleep exert far more force than grinding while awake.
People who realise that they clench or grind their teeth can take steps to break the habit. Usually, splint therapy is the main treatment. A thin plastic splint (nightguard) is made to fit over either the upper or lower set of teeth (usually the upper) and is adjusted to give the person an even bite. The splint reduces daytime and nighttime grinding, allowing the jaw muscles to rest and recover. The splint can also prevent damage to teeth that are under exceptional stress from the grinding.
A dentist may prescribe physical therapy which can consist of ultrasound treatment, electromyographic biofeedback, spray and stretch exercises, or friction massage. Transcutaneous electrical nerve stimulation also may help. Stress management, sometimes along with electrmyographic biofeedbcak, often brings dramatic improvement.
A dentist also may perscribe mediction. For instance, a muscle-relaxing drug may be prescribed to ease tightness and pain, particularly while a patient waits for a splint to be made. However, medications are not a cure, generally are not recommended for older people, and are prescribed for only a short time, usually for a month or less. Analgesics such as nonsteroidal anti-inflammatory drugs (aspirin, for example) also relieve pain. Dentists avoid prescribing narcotics because they can be habit forming. Sleeping pills may be used occasionally to help people who have trouble sleeping because of the pain.
In internal derangement, the disk inside the joint lies in front of its normal position.
In internal derangement without reduction, the disk never slips back into its normal position, and jaw movement is limited. In internal derangement with reduction, which is more common, 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, making a clicking or popping sound as it does. As the mouth closes, the disk slips forward again, often making another sound.
Symptoms and Diagnosis
Often, the only symptom of internal derangement is a clicking or popping sound in the joint when the mouth opens wide or the jaw shifts from side to side. As many as 20 per cent of all people have internal derangement that produces no symptoms except for these joint sounds. A dentist diagnoses internal derangement by performing an examination while the patient slowly opens and closes the mouth.
Treatment is needed when a person has jaw pain or trouble moving the jaw. If a person seeks treatment right after symptoms develop, a dentist may be able to push the disk back into its normal position. If the person has had the condition for less than three months, the dentist may apply a splint that holds the lower jaw forward. This splint keeps the disk in position, permitting the sup-porting ligaments to tighten. Over two to four months, the dentist adjusts the splint to allow the jaw back to its normal position, with the expectation that the disk will remain in place.
A dentist instructs a person with internal derangement to avoid opening the mouth wide - for instance, when yawning or biting into a thick sandwich. People with this condition need to stifle yawns, cut food into small pieces, and eat food that’s easy to chew.
If the condition can not be treated by nonsurgical means, an oral-maxillofacial surgeon may perform surgery to reshape the disk and sew it back into place. However, the need for surgery is relatively rare.
Often, people with internal derangement also have jaw muscle pain and tightness; after the muscle pain is treated, the other symptoms go away too. Dentists are more successful in treating muscle pain and tightness than in treating internal derangement.
Arthritis can affect the temporomandibular joints the same way it affects other joints. Osteoarthritis (degenerative joint disease), a type of arthritis in which the cartilage of the joints degenerates, is most common in older people. The cartilage in the temporomandibular joints is not as strong as the cartilage in other joints. Because osteoarthritis occurs mainly when the disk is missing or has developed holes, the person feels a grating sensation in the joint when opening and closing the mouth. When osteoarthritis is severe, the top of the jawbone flattens out, and the person can not open the mouth wide. The jaw may also be shifted toward the affected side, and the person may be unable to move it back. Even without treatment, most of the symptoms improve after a few years, probably because the band of tissue behind the disk becomes scarred and functions like the original disk.
Rheumatoid arthritis affects the temporomandibular joint in only about 17 per cent of people with this type of arthritis. When rheumatoid arthritis is severe, especially in young people, the top of the jawbone may degenerate and shorten. This damage can lead to sudden misalignment of many or all of the upper and lower teeth (malocclusion). If the damage is severe, the jawbone may eventually fuse to the skull (ankylosis), greatly limiting the ability to open the mouth. Rheumatoid arthritis usually affects both temporomandibular joints about equally, which is rarely the case in other types of temporomandibular joint disorders.
Arthritis in a temporomandibular joint also may result from injury, particularly injury that causes bleeding into the joint. Such injuries are fairly common in children who are struck on the side of the chin.
A person with osteoarthritis in a temporomandibular joint needs to rest the jaw as much as possible, use a splint or other device to control muscle tightness, and take an analgesic for pain. The pain usually goes away in six months with or without treatment. Usually, jaw movement is sufficient for normal activities, though the jaw may not open as wide as it used to.
Rheumatoid arthritis of the temporomandibular joint is treated with the drugs used for rheumatoid arthritis of any joint; these may include analgesics, corticosteroids, methotrexate, and gold compounds. Maintaining joint mobility and preventing ankylosis (fusion of the joint) are particularly important. Usually, the best way to accomplish these goals is by exercising under a physical therapist’s direction. To relieve symptoms, particularly muscle tightness, the person wears a splint at night that does not restrict jaw movement. If ankylosis freezes the jaw, the person may need surgery and, in rare cases, an artificial joint to restore jaw mobility.
Ankylosis is loss of joint movement resulting from fusion of bones within the joint or calcification of the ligaments around it.
Typically, calcification of the ligaments around the joint is not painful, but the mouth can open only about one inch or less. Fusion of bones within the joint causes pain and more severely limits jaw movement. Occasionally, stretching exercises help people with calcification, but people with calcification or bone fusion usually need surgery to restore jaw movement.
Hypermobiliry (looseness of the jaw) results when the ligaments that hold the joint together become stretched.
In a person with hypermobility, the jaw may slip forward completely out of its socket (dislocation), causing pain and an inability to close the mouth. This can happen repeatedly. When it happens, a helper should stand in front of the person, place the thumbs on the gums next to the lower. back teeth, and press first down and then back on the outer surface of the teeth. The jaw should snap back into position. The helper needs to keep the thumbs away from the chewing surfaces because the jaws close with considerable force.
Prevention consists of avoiding opening the mouth wide, so that the ligaments are not excessively stressed. Thus, the person should stifle yawns and avoid large sandwiches and other foods that require opening the mouth wide. If dislocations occur frequently, surgery may be needed to reposition or shorten the ligaments and make the joint tighter.
Abnormalities of the temporomandibular joint at birth are uncommon. Sometimes the top of the jawbone does not form or is smaller than normal.
Other times, the top of the jawbone grows faster or for a longer time than normal. These abnormalities can cause facial deformities and misalignment of the upper and lower sets of teeth. Only surgery can correct these problems.
Dr. Md. Shah Alam, MBBS
Writer is working as Resident Medical Officer in a Hospital in Riyadh, K.S.A.
- TMJ disorders and treatment - temporomandibular joint: Cosmetic dentistry guide
- What Causes TMJ Disorders: AAOMS.org
- Temporomandibular Joint Disorder: Pain Resource Centre
- TREATMENT FOR TMJ DISORDERS: McKinley Health Center (University of Illinois)
- Temporomandibular joint disorders are problems affecting the jaw joint: Patient UK
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