THE connection between the (lower) jaw and the skull is technically known as the temporomandibular joint (TMJ). It functions through five pairs of muscles attached to the facial bones. The structures (bones, muscles, ligaments and discs) that make it possible to open and close the mouth are very specialised, and are required to work together to enable you to chew, speak and swallow. The muscle pairs must work in proper balance, so that stress on both sides of the jaw is distributed as equally as possible.

The TMJ is considered very complex, because it can perform many different movements, including combinations of hinge and gliding actions. The juncture where the two joints meet has a disc that acts as a shock absorber for biting and chewing forces. Any problem that prevents this complex system of structures from working together properly may result in cycles of pain, spasm (cramp), muscle tenderness, and tissue and joint damage. This is known as temporomandibular disorder (TMD).

Most researchers agree that temporomandibular disorders are grouped into three main categories, as follows. A person may have one or more of these conditions at the same time.

Myofascial pain is the most common form of TMD. It involves pain in the muscles that control jaw function, the neck and the shoulder.

Internal derangement of the joint means a dislocated jaw, a displaced disc or injury to the condyle.

Degenerative joint disease includes osteoarthritis or rheumatoid arthritis in the jaw joint.

Symptoms that TMD sufferers have include:

• An ache in the area of the ear extending to the back of the head, into the neck and shoulders.
• Hearing a clicking or popping sound on opening and closing the mouth.
• Pain brought on by yawning, opening the mouth widely or chewing.
• Difficulty in opening the mouth and chewing (limited movement).
• Headaches that can mimic migraines, earaches, dizziness and neck aches.
• Jaw that ‘gets stuck’, locks or ‘goes out’.
• Tenderness of jaw muscles.
• A sudden change in the way the upper and lower teeth fit together.

A combination of one or all of these symptoms can also be present for other problems. There are no exact causes and symptoms of TMD, so diagnosis can be difficult. After guidelines have been established, it will be easier for health professionals to correctly identify TMD and make appropriate treatment choices for patients. It is important for your dentist to have a complete health and dental history to make a diagnosis. Regular dental X-rays and TMJ X-rays are not useful in diagnosing this disorder. Diagnostic techniques that include CT scans and MRI scans are usually needed unless the health professional strongly suspects arthritis or the pain and symptoms do not improve with treatment.

Some clear-cut causes of TMD are arthritis, trauma or severe stress. Unfortunately, TMD is usually a combination of factors and is not easily diagnosed. It is common for the disc in the temporomandibular joint to slip forward and click, pop or even get stuck for a moment. In the absence of jaw pain, this is a minor problem that does not require treatment. Stress often leads to teeth clenching or grinding, which may be a factor that starts the cycle of muscle pain and spasms. Many researchers feel that behavioural and physical factors all contribute to TMD. It is important to note that currently, we do not know the exact causes of this disorder.

Conservative (reversible) treatments include counselling or biofeedback training to reduce emotional stress; muscle massage, relaxants or tension monitors to aid in breaking the spasm-the-spasm cycle; short-term soft diets to give the jaw rest (avoiding movements such as yawning and gum chewing); physical therapy that focuses on gentle muscle-relaxing exercises; and short-term use of anti-inflammatory and muscle-relaxing drugs.