Temporomandibular Joint Disorder
(TMJD, TMJ or TMD) or TMJ Syndrome

is an umbrella term covering acute or chronic inflammation of the temporomandibular joint that connects the lower jaw to the skull. The disorder and resultant dysfunction can result in significant pain and impairment. Because the disorder has many facets the boundaries between several health-care disciplines — in particular, dentistry, neurology, and physical therapy offer a variety of quite different treatment approaches.

The temporomandibular joint is susceptible to many of the conditions that affect other joints in the body, including ankylosis, arthritis, trauma, dislocations. 

Signs and Symptoms

Signs and symptoms of temporomandibular joint disorder vary in their presentation and can be very complex. Often the symptoms will involve more than one of the numerous TMJ components: muscles, nerves, tendons, ligaments, bones and the teeth. Ear pain is a common symptom of temporomandibular joint disorder.

Muscles

Disorders of the muscles of the temporomandibular joint are the most common complaints by TMD patients. The two major observations concerning the muscles are pain and dysfunction. The dysfunction can present as a limitation of jaw movement ranging from minor to severe. In milder cases, the only representation may be joint sounds such as clicking or popping. These symptoms of TMD are often caused by over usage of the muscles. Common causes include chewing gum continuously, biting habits (fingernails and pencils), grinding habits, and clenching habits.

Muscle pain can sometimes be associated with trigger points in muscle tissue. These trigger points can be localized by digital palpation, both intra-orally and extra-orally. This is known as Myofascial pain syndrome.

Any dysfunction of the muscles may cause the teeth to bite with each other incorrectly. If teeth are traumatized by this they may become sensitive, demonstrating one of the many interplays between muscle, joint, and tooth.

Temporomandibular Joints

This is arguably the most complex set of joints in the human body. Unlike typical finger or vertebral junctions, each TMJ actually has two joints, which allow it to both rotate and to slide. With use, it is common to see wear of both the bone and cartilage components of it. Clicking is common, as are popping motions and deviations in the movements of the joint. It is considered a TMJ disorder when pain is involved.

In a healthy joint, the surfaces in contact with one another (bone and cartilage) do not have any receptors to transmit the feeling of pain. The pain therefore originates from one of the surrounding soft tissues. When the position from one of these areas is not aligned, the pain causes a reflex to limit the lower jaw's movement. Furthermore, inflammation of the joints can cause constant pain, even without movement of the jaw.

Due to close proximity of the ear to the temporomandibular joint, TMJ pain can often be confused with ear pain. Conversely, TMD is an important possible cause of secondary ear pain. Treatment of TMD may then significantly reduce symptoms of ear pain, as well as atypical facial pain.

The dysfunction involved is most often in regards to the relationship between the head of the lower jaw and the disc. The sounds produced by this misalignment are usually described as a "click" or a "pop" when a single sound is heard and as "crepitation" or "crepitus" when there are multiple, rough sounds.

Teeth

Disorders of the teeth can contribute to TMJ dysfunction. Tooth mobility and tooth loss can be caused by destruction of the supporting bone and by heavy forces being placed on teeth. Movement of the teeth affects how they contact one another when the mouth closes, and the overall relationship between the teeth, muscles, and joints can be altered.

Participating Factors

There are many external factors that place undue strain on the TMJ. These include but are not limited to the following:

Over-opening the jaw beyond its range for the individual or unusually aggressive or repetitive sliding of the jaw sideways or forward.  This may be due to:

Treatment

Restoration of the occlusal surfaces of the teeth

If the biting surfaces of the teeth or the supporting structures have been damaged due to dental neglect, periodontal diseases or trauma, the proper biting surface should be restored.

Pain Relief

While conventional analgesic pain killers such as NSAID's (Ibuprophen) provide initial relief for some sufferers, the pain is often from a number of possible causes, which may not respond well to these drugs.

Long-term approach

An approach to eliminating damaging habits involves the taking of a detailed history and careful physical examination. The medical history should be designed to reveal duration of illness and symptoms, previous treatment and effects, contributing medical findings, history of facial trauma, and a search for habits that may have produced or enhanced symptoms. Particular attention should be directed in identifying jaw habits, such as clenching or teeth grinding, lip or cheek biting, or positioning of the lower jaw in an edge-to-edge bite. All of the above strain the muscles of and results in jaw pain.

Treatment is oriented to eliminating oral habits, physical therapy to the muscles, and alleviating bad posture of the head and neck. A flat-plane full-coverage oral appliance, e.g. a stabilization splint, often is helpful to control bruxism (grinding) and take stress off the temporomandibular joint.

According to the National Institute of Dental and Craniofacial Research (NIDCR) of the National Institutes of Health (NIH), TMJ treatments should be reversible whenever possible. That means that the treatment should not cause permanent changes to the jaw or teeth. Examples of reversible treatments are:

What may be concluded is that there are various treatment modalities that a well-trained experienced dentist may employ to relieve symptoms and improve joint function. They include:

Exercise protocols, habit control, and splinting should be the first line of approach, leaving oral surgery as a last resort. Certainly a focus on other possible causes of facial pain and jaw immobility and dysfunction should be the initial consideration of the examining oral-facial pain specialist.