The Temporomandibular Joint (TMJ) is a paired joint where the mandible (lower jaw) meets the temporal bone (base of the skull) just forward of the ears. Since it is a paired joint, the right and left sides must function together in harmony. It is the only joint in the human body to have a rigid end point of closure…that is where the teeth make contact to limit jaw movement.
The normal movement of this joint is both a rotation and a sliding motion. As we begin to open our mouths, the rotation aspect of the movement begins and as we continue to open the mouth, the lower jaw actually begins to slide downwards and forward.
The basic components of this joint consist of bone, tissue, muscle, ligaments, tendons and a disk which acts like a small pillow or cushion, protecting the joint from wear, sort of like a shock absorber.
The disk is the source of lubrication which keeps the motion of the joint smooth. It has a concave surface which allows the condyle to nestle in place and it is held in place by numerous ligaments. Ligaments hold the skeleton together. They connect bone in the manner which allows them to move in harmony, they have a poor blood supply. Over-stretched or torn ligaments typically are caused by some type of trauma and they will not hold each of the pieces of the joint in place. Strain on these ligaments can be a source of pain and discomfort.
There are 27 muscles of the jaw that determine the position of the TMJ. The primary muscles involved in jaw closure are the Masseter muscle and the Temporalis muscle. The Masseter muscle starts below the cheek bone and runs down to the lower posterior edge of the mandible. The Temporalis muscle originates from the side of the skull (temple area) and connects to the cornoid process of the mandible. Its tendon runs along the anterior surface of the mandible. These two muscles are often tender in people who clench/grind their teeth.
Temporomandibular Joint Disorder (TMD) is characterized by signs and symptoms, including pain in the area of the TMJ and/or surrounding muscles, which often limits the mandibular range of motion. TMD is also defined as sounds or clicking causing pain. Symptoms may include; headache (68% of the population), neck/back/shoulder pain, clicking/popping sound, ear pain, visual disturbances, clenching/bruxing, fatigue, sleep disorder breathing, and depression.
Most TMD patients worsen with time. Slight clicking advances to more frequent clicking and eventually to jaw locking as the posterior ligaments continue to stretch, allowing the disc to move further and further out of position. When the disc has slipped too far forward or inward, the jaw will lock shut, often referred to as a "closed lock". Depending upon the severity of the problem there are several treatment options available to treat TMD. Muscle contraction and tension-type or temporal headaches are candidates for splint therapy.
Splint therapy consists of the placement of removable and/or fixed dental appliances, which protect to keep in place the injured body part. The purpose of this type of therapy is to reduce the inflammation and pain. This type of therapy will not restore all of the damaged or degenerated components.
Orthotic therapy is similar to splint therapy; however, an orthotic is used to support, align, prevent or correct deformities or improve the function of movable parts of the body. The goal of orthotic therapy is to provide the best condyle-fossa relationship possible, to decompress the joint that reduces the inflammation, and to restore correct muscle length bilaterally. Surgery is only recommended in about 2% of TMD cases.