Many conditions may cause temporomandibular joint (TMJ) disorders. Unless the symptoms of TMJ disorders occur suddenly, it may take a few recurrences to become aware of an underlying condition that periodically flares up causing pain and/or other symptoms.
Causes of TMJ Disorders
A few potential causes of TMJ disorders are discussed below.
- Parafunctional habits. Parafunctional or behavioral habits are a common cause of TMJ disorders. These include repetitive teeth clenching and/or grinding, also called bruxism. Such repetitive habits may be caused due to stress and other psychological factors, and may also disrupt other functions, such as sleep and/or mood. Repetitive trauma caused by parafunctional habits may result in wearing of teeth, internal derangement of the TMJ, and TMJ muscle strain, spasm, and/or fatigue (myofacial pain and dysfunction). Parafunctional behaviors leading to TMJ disorders may be involuntary in some cases, such as when they occur during sleep or while thinking about something else. These habits may also sustain TMJ disorders.
- Malocclusion. Misaligned teeth due to conditions such as an anterior open bite (front teeth do not come together), a protrusion of the upper front teeth greater than 6 to 7 millimeters, cross-bite, missing teeth, and/or faulty dental fillings and prosthesis may cause TMJ disorders.1
- Habitual chewing side syndrome. This syndrome refers to the negative effects of constantly chewing on the same side. Over time, the load on the TMJ of the non-chewing side may increase, along with a change in the structure of the condylar cartilage.
- Arthritis of the TMJ. Arthritis affecting the TMJ may be infectious, traumatic, degenerative, rheumatoid, or chronic. Internal derangement of the TMJ's articular disc is common in most types of arthritis and clicking sounds may be followed by grating sounds over time as the condition worsens.
- Facial trauma. Trauma to the TMJ from motor vehicle accidents may cause misaligned teeth, whiplash injury to the joint, and/or fracture of the mandibular condyle. External trauma may also cause fibrous adhesions, fusion, and other conditions disrupting the balance of the TMJ.
- Estrogen hormone. Estrogen may cause cartilaginous breakdown in the TMJ resulting in TMJ disorders in some women and men.2,3
- Other causes. Hypermobility or hypomobility of the TMJ, tumors, lack of blood supply to the TMJ, resorption of bone in the TMJ, prior surgery in the TMJ or surrounding structures, ankylosing spondylitis, and genetic factors may also cause TMJ disorders.
Sometimes, TMJ disorders may also develop from unknown causes.
Risk Factors for TMJ Disorders
The presence of certain risk factors and conditions may increase the likelihood of developing TMJ disorders. A few examples include:
- Psychological factors. Psychological conditions, such as anxiety and/or depression are common risk factors of TMJ disorders.
- Chronic pain conditions. TMJ disorders may be associated with certain chronic pain conditions, such as tension headache, chronic fatigue syndrome, fibromyalgia, functional dyspepsia, painful bladder syndrome, and irritable bowel syndrome. The exact reason for the development of TMJ disorders with these conditions is unknown, and the TMJ disorder may develop before or after the associated condition develops.
- Sleep apnea. TMJ disorders are closely related to obstructive sleep apnea, a condition resulting in intermittent blockage of airflow during sleep. The likelihood of TMJ disorders is three times more in individuals who are likely to have obstructive sleep apnea.4
- Lengthy and/or repetitive dental treatments. Holding the mouth wide open during dental procedures, such as extraction of molars, orthodontic treatment, and/or dental implants may cause pain and discomfort in the TMJ and may become chronic if left untreated.
- Female sex. TMJ disorders are more common among women than men.5
TMJ disorders usually affect adults between the ages of 20 and 40 years,5 but these disorders may occur at any age, including infancy and childhood.