Temporomandibular joint (TMJ) syndrome or TMJ joint disorders are medical problems related to the jaw joint. The TMJ connects the lower jaw (mandible) to the skull (temporal bone) in front of the ear. Certain facial muscles control chewing. Problems in this area can cause head and neck pain, a jaw that is locked in position or difficult to open, problems biting, and popping sounds when the patient bites.
The TMJ is comprised of muscles, blood vessels, nerves, and bones. There are two TMJs, one on each side of the jaw. Muscles involved in chewing (mastication) also open and close the mouth. The jawbone itself, controlled by the TMJ, has two movements: rotation or hinge action, which is opening and closing of the mouth, and gliding action, a movement that allows the mouth to open wider. The coordination of this action also allows an individual to talk, chew, and yawn.
When the mouth is opened, the rounded ends of the lower jaw (condyles) glide along the joint socket of the temporal bone. The condyles slide back to their original position when the mouth is closed. To keep this motion smooth, a soft disc of cartilage lies between the condyle and the temporal bone. This disc absorbs shock to the temporomandibular joint from chewing and other movements. Chewing creates a strong force. This disc distributes the forces of chewing throughout the joint space.
TMJ syndrome can be caused by trauma, disease, wear due to aging, or habits. Trauma is divided into micro trauma and macro trauma. Micro trauma is internal, such as bruxism (grinding the teeth) and clenching (jaw tightening). This continual hammering on the temporomandibular joint can change the alignment of the teeth. Muscle involvement causes inflammation of the membranes surrounding the joint. Teeth grinding (bruxism) and clenching are habits that may be diagnosed in people who complain of pain in the temporomandibular joint or have facial pain that includes the muscles involved in chewing (myofascial pain). Macro trauma, such as a punch to the jaw or impact in an accident, can break the jawbone or damage the disc.
Teeth grinding (bruxism) as a habit can result in muscle spasm and inflammatory reactions, thus causing the initial pain. Changes in the normal stimuli or height of the teeth, misalignment of the teeth, and changes in the chewing muscles may cause temporomandibular joint changes. Generally, someone who has a habit of grinding his or her teeth will do so mostly during sleep. In some cases, the grinding may be so loud that it disturbs others.
Someone who clenches continually bites on things while awake. This might be chewing gum, a pen or pencil, or fingernails. The constant pounding on the joint causes the pain. Stress is often blamed for tension in the jaw, leading to a clenched jaw.
Like other joints in the body, the jaw joint is prone to undergo arthritic changes. These changes are sometimes caused by breakdown of the joint (degeneration) or normal aging. Degenerative joint disease causes a slow progressive loss of cartilage and formation of new bone at the surface of the joint. Cartilage destruction is a result of several mechanical and biological factors rather than a single entity. Its prevalence increases with repetitive micro trauma or macro trauma, as well as with normal aging. Immunologic and inflammatory diseases contribute to the progress of the disease.
Rheumatoid arthritis causes inflammation in joints and can affect the TMJ, especially in children. As it progresses, the disease can cause destruction of cartilage and erode bone, deforming joints. It is an autoimmune disease involving the antibody factor against immunoglobulin G (IgG). Chronic rheumatoid arthritis is a multisystem inflammatory disorder with persistent symmetric joint inflammation.
Pain in the facial muscles and jaw joints may radiate to the neck or shoulders. Joints may be overstretched. The patient may experience muscle spasms from TMJ syndrome and feel pain every time the patient talks, chews, or yawns. Pain usually appears in the joint itself, in front of the ear, but it may move elsewhere in the skull, face, or jaw. TMJ syndrome may cause ear pain, ringing in the ears (tinnitus), and hearing loss. Sometimes people mistake TMJ pain for an ear problem, such as an ear infection, when the ear is not the problem at all.
When the joints move, the patient may hear sounds, such as clicking, grating, and/or popping. Others may also be able to hear the sounds. Clicking and popping are common. This means the disc may be in an abnormal position. The face and mouth may swell on the affected side. The jaw may lock wide open (then it is dislocated), or it may not open fully at all. Also, upon opening, the lower jaw may deviate to one side. The patient may be favoring one painful side or the other by opening the jaw awkwardly. These changes could be sudden. The patient’s teeth may not fit properly together, and their bite may feel odd. Patients may have trouble swallowing because of the muscle spasms or experience headache and dizziness caused by TMJ syndrome.
Many people, more women than men, have TMJ syndrome. However, the full TMJ disorder develops in only a few. Early therapy starts simply with resting the jaw, using warm compresses (ice packs at first if an injury is present), and pain medication. Jaw rest can help heal temporomandibular joints. Eat soft foods. Avoid chewing gum and eating hard candy or chewy foods. Do not open the mouth wide. Stress-reduction techniques can help the patient manage stress and relax the jaw along with the rest of the body.
The doctor may fit the patient with a splint or bite plate. This is a plastic guard that fits over the upper and lower teeth, much like a mouth guard in sports. The splint can help reduce clenching and teeth grinding, especially if worn at night. This will ease muscle tension. If conservative and noninvasive techniques do not work, more invasive techniques are considered.
For example, under local anesthesia, two needles can be inserted in the temporomandibular joint to wash it out. One needle is connected to a syringe filled with a cleansing solution, and the fluid exits via the other syringe. This procedure can be done in the office. Most people find relief from the pain and return to almost normal. Sometimes, pain medication can be injected into the joint in a similar procedure. Alternatively, a simple injection of cortisone medication can be very helpful in relieving inflammation and pain.
A last option, surgery, is often irreversible and should be avoided when possible. If necessary, surgery can be used to replace the jaw joints with artificial implants. The National Institute of Dental and Craniofacial Research (NIDCR) advise that other irreversible treatments are of little value and may not cure the problem. These include orthodontia to change the bite, restorative dentistry, and adjustment of the bite by grinding down teeth to bring the bite into balance.