Predisposing factors

Gender

TMD effects women more than it does men. This is due partly to the differences in bone and muscle densities between the two sexes, and partly to differences in psychological outlook and worldview. Studies show that women are more responsive to emotional imagery and have a greater cardiovascular response to stress than men. In addition hormones have an enormous influence on pain modulation. All things combined, women are more likely than men to brux (clench and grind their teeth) and the bruxing is more likely to cause pain and dysfunction.

Age

TMD is NOT forever! Like most natural phenomena, the occurrence of serious TMD happens along a "bell shaped curve" with the vast majority of the sufferers falling between the ages of 25 to 45. This implies that it is associated with psychological and physiological variables which change throughout life. As a patient ages past the critical age of 45, these variables tend to change and interact in such a way that the problem lessens and eventually vanishes, even without any treatment at all. TMD does occur in younger or older patients, but with decreasing frequency as age decreases or increases from the mean age of 35.

Posture

In a normal relaxed state, the lower jaw, affected by gravity, tends to drop into eccentric positions away from the position in which the upper and lower teeth would normally come together. This is especially true in persons who tend to hold their heads so that their jaw line is not parallel to the floor (perpendicular to the force of gravity). Normally, this causes no problems, however persons who grind or clench their teeth may grind in these unusual positions. This places unequal and eccentric pressures on their face, head and neck muscles as well as the TM Joints. Think of the receptionist who keeps her computer monitor to her left (so as not to block the view of a client standing in front of her), her keyboard in the pullout drawer under the desk in front of her, and who talks on the phone keeping the receiver tucked between her right shoulder and her right ear. Try that position yourself for a few minutes and see how your neck and head feel.

Occlusion--the way your upper and lower teeth come together

In most people, the upper and lower teeth naturally line up so that when they come together, the TM Joints are sitting normally in their sockets. Whenever something disturbs the way they come together, say a new filling or a lost tooth, this can effect the relative positions of the two TM Joints. Grinding or clenching in these eccentric positions can cause muscle splinting (cramping) and joint problems. There is a complex, dynamic balance between the way that the teeth come together, the muscles that work the jaws, the TM Joints, and their relationship to the posture of the head and neck. A change in any part of the system effects all others and changes the balance. (For more on this subject, Click on the icon on the right to see my page on occlusion. Read about my patient, Popeye here.)

Sleep disorders

Many people do not sleep well due to several physiologic factors (see my section on snoring and sleep apnea). Nighttime muscle hyperactivity can lead to nighttime bruxing (grinding and clenching) and thus to morning headaches, neckaches, earaches and tooth sensitivity. There is some disagreement about whether nighttime bruxing is a problem associated with sleep apnea, or whether it is a sleep disorder in its own right.

Life stressors

Stress is an ever present problem in our society and is a prime reason why people unconsciously grind and clench their teeth. The next section explains why bruxing (grinding and clenching) causes so many problems and is the root cause of TMD.