The Temporomandibular Joint

The temporomandibular joint is unique. It is a ginglymo-diarthrodial joint, which is also linked to its contra-lateral counterpart. Such daunting philology suggests complexity and this indeed is the case.

In general, there are two groups of patients with temporomandibular joint disorders. Those with normal anatomy, but abnormal function, and those with abnormal anatomy whose function may be abnormal.

Temporomandibular joint dysfunction is ill-understood, but may affect as many as 40% of the population at some time and is more common in females. It may begin in adolescence with pain and clicking in the joints which often recovers, never to recur. A small group have further problems, some continuing into early adult life before symptoms subside. A very small percentage of these develop increasing symptoms in their 40's and 50's and may end with chronic facial pain. A second group does not recover after the first episode and eventually develops continuous discomfort which may profoundly upset their lives. It is this group for whom various hypotheses have been formulated.

Some regard the dental occlusion as the "third joint surface" and postulate that abnormalities in the way teeth fit together generate disharmony in movement of the joints with symptoms caused by muscle spasm, made worse by emotional upset which can produce an increase in muscle tone.

Psychological causes and stress can increase temporomandibular joint symptoms and TMJ dysfunction patients have higher catecholamine levels than controls and indeed treatment with anti-depressants or sedation improves many of these patients.

Many feel this may be the basis of dysfunction symptoms with pain thought to be produced by masticatory muscle spasm. Abnormal habits, playing wind instruments, occlusal disharmony, over-contraction and fatigue of muscles influence it. Conservative management of the condition includes exercises, advice about diet, altering the dental bite with splints and sedation or anti-depressants.

Whichever the theory followed, treatment involves conservative measures first and about 40-50% of patients will be improved by these alone.

The second main group of patients are those with abnormal anatomy. The simplest is meniscus displacement and in such patients plain radiography is often of little use if there is no hard tissue abnormality. CT scanning is similar, if more accurate. MRI scanning will demonstrate the position of the meniscus and shows bony tissues of the joint.

Surgical treatment on these patients must only be undertaken after very careful evaluation and trial of conservative treatment. Surgery can be divided into two types: reparative and reconstructive. Repair involves restoring the meniscus to its correct position, repairing it if necessary. In the past, surgery for TMJ disease was less scientific and the results were appropriately variable, but now there is deeper understanding, better investigation and sub-specialisation of surgeons which appears to improve outcome.