Understanding Temporomandibular Joint Dysfunction
What Is TMJ?
TMJ is an abbreviation for temporomandibular joint dysfunction. The temporomandibular joint is the joint that connects your mandible (lower jaw) to your skull. It is located just in front of your ear. When the jaw is misaligned it can cause a wide array of symptoms which is why TMJ dysfunction is referred to as a syndrome, meaning a collection of symptoms. Symptoms include jaw pain, headaches, tooth pain, neck pain, sinus pain, eye pain, visual disturbances, etc. (see Associated Medical Disorders).
The dental profession as a whole is very poorly educated on TMJ. Generally, most dental school curriculums give TMJ very little attention. The schools do not know “what is TMJ”.
TMJ treatment is further complicated in that there is a very long-standing controversy as to the cause, and subsequently what comprises proper treatment. The first camp believes that TMJ is psychosomatic—stress-induced. The other camp believes that it is due to a misaligned jaw. If you believe the first, then the proper treatment is psychotherapy, stress management, night guards, and physical therapy. If you believe in the latter, then the preferred treatment is jaw repositioning with appropriate appliances designed to align the jaw. My clinical experience has been that 95% of the cases fall into the latter classification.
I believe this controversy continues in large part due to the fact that dentistry is based on structure, not function. Dentistry does not have a functional model of ideal occlusion (see New model of Occlusion), only a structural model (class I occlusion).
What Causes TMJ?
I believe most cases of TMJ are caused by misaligned jaws, not stress. When the jaw is misaligned one handles stress poorly. There are a number of situations that can cause a person to develop a misaligned jaw: deviated septum, genetics, allergies, poor orthodontics, poor dental work, missing teeth, etc.
How Do You Diagnose TMJ?
Typically, upon examination of a TMJ patient I find that there is a substantial vertical height deficiency from the inherited structure which necessitates that the lower jaw be pulled back in order to get the teeth together, thus causing compression in the TMJ and subsequent TMJ pain. Clinically this is determined by 1)feeling the excess compression in the TMJ by sticking your finger into your ear lightly and biting down. On a normal person, the condylar head is not palpable. (2) Have the patient count from sixty to seventy. Often with a misaligned jaw, the lower jaw thrusts with “s” sounds (not ideal). (3) Have the patient open wide and close on a tongue blade (stick). Most patients with TMJ bite significantly more forward with the tongue blade than in their normal bite. The tongue blade keeps the front teeth from hitting ( hitting the front teeth would normally cause the jaw to bite back- compressing the TMJ). (4) Take X-rays or MRI if necessary.
X-ray of TMJ
Together, this information can very quickly determine if the TMJ is compressed.
Fixing the compression will get rid of symptoms and joint pain rapidly. This is done by inserting an appliance (twin block appliance pictured) in the mouth that builds the back teeth taller so that the jaw does not close up into the joint so far (see sample picture). In the picture, overbite has been eliminated and the lower jaw is slightly forward of the upper. Eventually, the case will be stabilized in the final determined therapeutic position by orthodontic eruption of the back teeth.