TMJ Causes & Dysfunction

The initials TMJ refer to the “temporomandibular joint,” or jaw joint, where the lower jaw and upper jaw come together. The TMJ is located in front of the ears and is the most complex joint in the human body. This joint contains a complex of blood vessels, nerves, muscles and bones that can all be affected by an injury, clenching or grinding of the teeth or a bad bite. When the joint is not functioning properly some call it TMJ dysfunction or TMD, temporomandibular disfunction.

Many people have experienced some form of TMJ at some point in their lives. Studies estimate that 25% to 35% of the adult population has ongoing TMJ problems but most are undiagnosed and untreated. Women generally report a higher incidence of TMJ, but damage to the bone, teeth and gums can occur in both men and women. As far as age goes, bite problems and TMJ problems can occur at any time from teenagers to octogenarians.

Note that a TMJ problem is NOT defined by the presence of popping or clicking but by any irregularity in movement of the jaw. This can sometimes be seen when standing in the mirror and opening and closing the mouth. If the lower jaw does not open straight but veers to one side or another, a TMJ problem exists, even if no symptoms are occurring.

TMJ dysfunction can cause a variety of symptoms including:

• Headaches
• Migraines
• Noises coming from the joint, including clicking, popping, or grinding
• Jaw pain
• Pain in the ear
• Pain in the face
• Ringing in the ears (tinnitus)
• Pain or spasm in the neck or shoulder muscles
• Shortened teeth from grinding
• Inability to open very wide
• A change in your bite

The Cause of TMJ Problems
Absent a blow to the jaw, TMJ problems are the result of an improper bite or occlusal disease. Simply put, when the teeth are not coming together properly, they are unable to support the facial muscles. This places excessive strain on the muscles, which results in pain in the face. In turn, the facial muscles recruit muscles of the neck, shoulders and upper back to help reduce some of the strain. This causes stress and pain in these muscles as well. These muscles are then forced into a strained position, resulting in pain throughout the face, head, arms, shoulders, and back. And most incredibly, this may not be felt as spasm or tension but as toothache, bone loss, loose teeth, sensitive teeth, neck pain, facial pain, ear problems, and headaches.  However, this need not occur in most cases because a dentist specializing in the bite will have this as part of their standard examination.

Healthy and Unhealthy Jaw Joints
To understand the TMJ and its potential problems, a short discussion of its movements is necessary.
The TMJ, like all joints in the body, consists of two bones and a disc between them. In the case of the TMJ it is the back part of the upper jaw and the head of the lower jaw that are separated by the cartilage disc. What is unique about this joint is that it is the only joint that can move in 3 dimensions; all other joints in our body can only move in one or two dimensions.

As we open, because the upper jaw is fixed, it is the lower jaw that moves. A healthy jaw is properly aligned in the thickest part of the disc and starts opening by rotating on the disc for about ½ inch of the opening and then moves forward (translates) for the remainder of the opening with the disc moving forward along with it. This joint, as all joints, includes a complex set of muscles, ligaments, and tendons that must act in tandem with the opening muscles (shown below in blue). Problems occur when any part of this movement, whether it is when we open, chew our food, or even grind or clench our teeth, is altered by an unstable bite. It is then that the disc will be damaged or perforated and the muscles will go into spasm causing pain in one or more areas of the head and neck. The proper correction for a TMJ problem must involve stabilizing the bite so the joint will not receive the incorrect forces that cause the problem in the first place.

Here is a diagram of a healthy joint. Note how the red lines indicate that the lower jaw is seated in the proper place anatomically and in the thickest part of the disc ( yellow).

The following set of diagrams depicts the progression of a TMJ problem, from the initial displacement of the joint to a tear of the TMJ disc. Popping and clicking can come most any time when enough damage to the disc occurs. The potential end result can be locking of the jaw open or closed and a tearing of the disc which leads to arthritis in the joint. Pain can occur in the neck, head, jaw, teeth, face, shoulders and upper back due to a TMJ problem. In fact, many people who have chronic headaches and migraines are being treated with drugs yet the real trigger for them is the muscle tension and spasm caused by a TMJ problem.

In this diagram, when the mouth is closed, the joint is already somewhat out of position and not on the thickest part of the disc as seen by the misalignment of the red lines. This occurs from an unstable bite that moves the joint out of place.

As the mouth is opened, the lower jaw moves forward. Here, wear in the center of the disc (yellow) has occurred as well as a bulge in the disc just in front of the head of the lower jaw.

Over time, the wear on the disc gets worse and the disc thins out in some areas and bulges in others.

This diagram shows the jaw being pulled over the bulge as it opens further. As this occurs, so does the popping and clicking of the joint(s) which is a definite sign that the joint is damaged.

This diagram shows what is termed an “open lock”. It occurs when the lower jaw cannot be pulled over the disc bulge and prevents further opening at that point.

Of course, this is the end result of long standing disc wear and TMJ dysfunction.

The most important point about TMJ dysfunction is that is related to the bite; when the bite is corrected the joint stabilizes, symptoms moderate or disappear, and the joint is allowed to heal.

Clicking and Popping of the TMJ
A normal, healthy TMJ is quiet during function. The movement of the jaw during opening and closing is smooth without any sliding to one side or sudden changes in direction. When the muscles of the TMJ are over contracted or unhappy, the jaw will often deviate to one side or deflect due to this abnormal muscle contraction.
The condyle (head) of the lower jaw sits in what is known as the glenoid fossa (receptacle) of the upper jaw. This is the socket part of the upper jaw where the hearing and balance mechanisms are housed.
An unstable bite, accident, or clenching or grinding of the teeth can damage the ligaments holding the disc in place. This results in the disc slipping out of its proper position as shown in the diagrams above results in a clicking or popping sound.

Further progression of this trauma can lead to an inflammatory process. If the tissue surrounding the disc is severely damaged, the upper and lower jaw bone can contact each other during opening. Over time, the bone surfaces can become rough, which results in a grinding sound when opening and closing the jaw. This is known as crepitis, and over time, can lead to arthritis of the joint.

In some cases, the disc can get stuck in front of the head of the lower jaw. This results in the open lock as noted above. Interestingly enough, the disc usually slips back silently when the jaw is closed.