HEADACHE AND FACIAL PAIN: TEMPOROMANDIBULAR JOINT DISORDERS: CAUSES OF TMD

Causes of temporomandibular joint disorders (TMD) are unclear — TMD usually involves more than one symptom and rarely has a single cause. Experts believe TMD results from several factors acting together, including jaw injuries (trauma) and joint disease (arthritis).

Tooth clenching and grinding (called bruxism) and head/neck muscle tension have not been scientifically proven to be a cause of TMD, but they may make TMD symptoms worse or last longer. Bruxism and head and neck muscle tension often need to be controlled to reduce and manage TMD symptoms.

It is important for people with TMD to understand that the disorder can be chronic in nature. Many factors, such as stress, psychological health and emotional stability can influence how severe a person's symptoms are and how long they last. Because there is no quick fix or immediate cure for TMD, the most successful and scientifically supported treatments focus on self-management and control of factors that make the disorder worse.

Factors Associated With TMD

Trauma: Direct trauma to the jaws has been scientifically associated with the onset of TMD symptoms. Direct trauma to the jaws 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 anesthesia and surgical procedures of the mouth, throat, esophagus and stomach can traumatize the TMJs.

Abnormal habits: Habits such as tooth/jaw clenching, tooth grinding (bruxism), lip biting, fingernail biting, gum chewing and abnormal posturing of the jaws are common and have not been proven to cause TMD. These jaw habits often are associated with TMD and may be contributing factors that make ongoing TMD symptoms worse and/or last longer.

Occlusion: Dental occlusion refers to the way the teeth fit together or the bite. Historically, dental professionals believed that abnormal bite (called malocclusion) was a frequent cause of TMD, but recent research studies do not support this. Large studies have shown that most patients with TMD have normal occlusion and the majority of people with malocclusion do not have TMD. Poor occlusion can be a contributing factor in the etiology of TMD but it is not usually a significant single cause.

Psychological factors: Many patients with TMD say that their symptoms begin or become worse when they experience depression, anxiety or an increase in emotional stress. Scientific studies show that many patients with TMD experience higher levels of depression or anxiety than people without the disorder. Doctors and dentists do not know whether depression or anxiety is present before the onset of TMD and contributes to its cause, or whether the chronic pain associated with TMD leads to depression and anxiety. Many patients will increase their level of tooth clenching and grinding when they experience emotional stress, psychological imbalance or pain.

Diseases of the TMJs: Several types of arthritis may develop in the TMJs like any other joint in the body. It is common for osteoarthritis to be present in the aging population. Many other diseases such as Parkinson's disease, myasthenia gravis, strokes and amyotrophic lateral sclerosis (Lou Gehrig's disease) may lead to excessive or uncontrollable jaw movements. Diseases such as tetanus (lock jaw) may lead to uncontrolled jaw muscle contracture.

Other factors: Abuse of drugs and the use of certain prescription medications can affect the central nervous system and muscles and can contribute to TMD.