Trauma: Direct trauma to the jaws has been scientifically associated with the onset of TMD symptoms. Direct trauma can occur from a blow to the jaw, hyperextension or overstretching of the jaw, and in some cases, compression of the jaw. Lengthy or forceful dental procedures, intubation for general anesthetic and surgical procedures of the mouth, throat, and upper GI track (esophagus and stomach) can traumatize the temporomandibular joint.

Abnormal Habits: Habits such as tooth/jaw clenching, tooth grinding, lip biting, fingernail biting, gum chewing, and abnormal posturing of the jaws are often associated with TMD and may be contributing factors that perpetuate and aggravate ongoing TMD symptoms.

Occlusion: Dental occlusion refers to the bite, or the way the teeth fit together. Historically, the dental profession has viewed malocclusion (abnormal bite) as the only causative factor in TMD. In later years, the research focused more broadly on the bio-psychosocial theory of TMD. For instance, in large generalized population studies, the majority of people with malocclusion do not have TMD.

However, very recently, in focused studies of patients with existing TMD, occlusion is shown to be a significant factor, whether causal or perpetuating, along with many other significant factors. While occlusion may not be the only cause of TMD as historically thought, it is responsible along with other factors in causing TMD. It is anatomically impossible to deny the existence of teeth, their supporting nerves, and bone support; therefore, teeth cannot be avoided in the total treatment of TMD. As an integral part of the stomatognathic system, teeth will always contribute, to a variable degree, to the cause of TMD or pain in each patient.

Psychological Factors: Many patients with TMD report onset of jaw dysfunction symptoms or aggravation of preexisting TMD symptoms with increases in emotional stress, such as depression or anxiety. Scientific studies indicate that many TMD patients experience levels of depression or anxiety that are higher than the non-TMD population. Although it has not been established whether depression or anxiety is present prior to the onset of TMD and contributes to its cause, or whether the chronic pain associated with TMD leads to depression and anxiety, it is likely that all three of these scenarios exist variably from patient to patient. Many patients increase their level of tooth clenching and grinding when they experience emotional stress, depression, or pain.

Diseases of the TMJs: Several types of arthritis may develop in the TMJs, as with any other joint in the body. It is common for osteoarthritis to be present in the aging population, resulting in an anterior open bite. This anterior open bite can routinely be addressed without surgery and/or orthodontics.

Many other diseases, such as Parkinson's disease, Myasthenia Gravis, strokes, and Amyotrophic Lateral Sclerosis (Lou Gehrig's Disease), and tetanus may lead to excessive or uncontrollable jaw movements.

Other Factors: Abuse of drugs and the use of certain prescription medications such as SSRI antidepressants can affect the central nervous system and muscles to contribute to TMD.

* Portions of this material provided courtesy of the National Naval Medical Center in Bethesda, MD; Story Number: NNS020307-05.