TMJ Overview

Temporomandibular joint (TMJ) syndrome or TMJ joint disorders are structural problems related to the jaw joint. The TMJ connects the lower jaw (mandible) to the skull (temporal bone) under your ear. The attatching 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 you bite.

The TMJ is comprised of muscles, cartilage, nerves, and bones. You have 2 TMJs, one on each side of your jaw.

The muscles involved open and close the mouth. The jawbone itself, controlled by the TMJ, has 2 movements: hinge, which is opening and closing of the mouth, and glide, a movement that allows the mouth to open wider. The coordination of this action also allows you to talk, chew, and yawn.

• If you place your fingers just in front of your ears and open your mouth, you can feel the joint and its movement. When you open your mouth, 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 you close your mouth. To keep this motion smooth, a soft disc 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 Causes

TMJ can be caused by trauma, disease, wear-and-tear, or bad habts. Trauma is divided to microtrauma and macrotrauma. Microtrauma 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). Macrotrauma, such as a punch to the jaw or impact in an accident, can break the jawbone or damage the disc.

• Bruxism: Teeth grinding 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.

• Clenching: 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.

• Osteoarthritis: Like other joints in the body, the jaw joint is prone to have 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 microtrauma or macrotrauma, as well as with normal aging. Immunologic and inflammatory diseases contribute to the progress of the disease.