Temporomandibular disorders (TMD) involves the two joints that attach the lower jaw (mandible) to the skull. These two joints open and close the mouth, and are located directly in front of your ears.

Adult Skull Showing Temporomandibular Joint

Adult Skull Showing TMJ and Muscles
© 2009 Nucleus Medical Art, Inc.

You may have TMD if:

  • The temporomandibular joints (TMJ) are chronically inflamed and sore
  • The muscles that work the temporomandibular joints are regularly in spasm
  • The cushioning disc that should rest between the temporomandibular joint and the skull becomes worn out or displaced

Researchers do not exactly know what causes TMD. Some people have had accidents or injuries involving their jaw, but many others have had no such incident. Some of the possible causes include:

  • Grinding the teeth or clenching the jaw in response to stress (known as bruxism )
  • Arthritis of the temporomandibular joint
  • History of injury or trauma to the joint
  • Facial bone defects
  • Misalignments of the jaw or of the bite

Enlargement of TMJ With Jaw Open

Enlargement of TMJ with Open Jaw
© 2009 Nucleus Medical Art, Inc.

TMD symptoms may originate within the joint itself (least common) or from the muscles that surround the joint. The treatment of these two variants of TMD may differ. Recent research suggests that genetic factors may be associated with TMD symptoms.

Some research suggests that as many as 70% of all adults have at least one sign of TMD during physical or dental exam of the temporomandibular joints. However, only about 25% of all adults describe accompanying symptoms, and only about 5% seek treatment for their symptoms.

What are the risk factors for TMD?
What are the symptoms of TMD?
How is TMD diagnosed?
What are the treatments for TMD?
Are there screening tests for TMD?
How can I reduce my risk of TMD?
What questions should I ask my doctor?
What is it like to live with TMD?
Where can I get more information about TMD?