Whether TMD or trismus, jaw trouble needs attention

Dear Doctor: I had trouble opening my mouth wide when I was getting my teeth cleaned, and the hygienist said it could be TMJ. But my sister, who is a chiropractor, says she thinks it’s a muscle spasm. What is TMJ, anyway?

Dear Reader: TMJ refers to the temporomandibular joint, which connects the jaw to the skull. We each have two, one on each side of the jaw. These are the structures that allow us to open and close our jaw, move it from side to side and back to front. The temporomandibular joint, which is a sliding hinge joint, is a complex and delicate mechanism. It gets almost nonstop use as we speak, chew, yawn, smile and swallow. For some people, the joint continues to get a workout throughout the sleep cycle as they clench their jaws or grind their teeth.

When the joint stops working properly, it’s known as a temporomandibular disorder, or TMD. However, this type of malfunction has widely come to be referred to simply as TMJ.

Symptoms of a TMJ disorder can range from quite mild, such as an occasional clicking sound while chewing, to severe enough to interfere with eating or speaking. Someone having problems with this joint may experience tenderness or pain within the joint itself, in or around the ear, or in other areas of the face. The joint may make crackling or popping sounds when in motion, and it can lock, making it difficult, or even impossible, to fully open or close the mouth. Malfunction in the joint can cause tinnitus, which is a ringing sound in the ear, or other noise that isn’t caused by an outside stimulus.

Your sister’s suggestion that your range-of-motion problem is related to the muscles in the jaw refers to a condition known as trismus. It’s sometimes called lockjaw, which brings to mind the muscle contractions associated with tetanus. However, these days, trismus refers to any muscle spasm within the temporomandibular joint that limits range of motion. It occurs when the muscles we use in chewing contract and don’t release.

Eve Glazier, M.D. and Elizabeth Ko, M.D

When someone can’t open his or her mouth wider than 1.3 inches, they are considered to have trismus. It can be caused by damage or injury to the jaw, and it can also arise as a result of TMD. Symptoms include the reduced range of motion you experienced, pain or cramping in the jaw that occurs with or without movement, and pain or difficulty when exerting pressure, as when eating.

Whether or not your jaw problem is due to TMD or trismus, we urge you to see your doctor or a TMD specialist for diagnosis. This will include a medical history, including information about recent dental procedures or physical injuries, an exam to rule out structural or other abnormalities, and measurements of how wide you can open your mouth. Depending on what is found, additional imaging studies may be requested. Treatment of TMD and trismus can include resting the jaw with a soft food diet, medications for pain, muscle relaxers, exercises to gently stretch the jaw, behavioral therapy and devices to prevent nighttime clenching. In rare cases, surgery may be required.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)


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