Harvard Health Blog
Unlocking the lock jaw: Temporomandibular joint dysfunction
The temporomandibular joint (TMJ) is one of the most heavily utilized and underappreciated joints in the human body. Mechanically, the TMJ is what allows you to open and close your mouth, and to a lesser extent, extend and move your jaw from side to side. Functionally, it facilitates eating, talking, and facial expressions. Without a TMJ, McGruff the crime dog would not be able to "Take a bite out of crime," and Jaws would have never become a savage predatory superstar of the deep blue sea. Just kidding. We all know from "Shark Week" that sharks do not actually have a TMJ, but you get the idea.
Structurally, the TMJ is a complex joint that involves multiple muscles working in concert with uniquely shaped cartilage to allow for the powerful actions of chewing, as well as the fine movements involved with speech. Like so many parts of the human body, the TMJ usually only receives attention when something goes wrong.
The grind of grinding
Grinding of the teeth, also known as bruxism, is a very common problem. For many people this occurs at night during sleep (nocturnal bruxism). Since it occurs during sleep, many people are unaware that they're even doing it, but the noise generated can be unbearable for a sleep partner. People with nocturnal bruxism often wake up the next morning with tightness and soreness of the jaw muscles. Bruxism over time can cause destruction of tooth enamel, the formation of gaps between teeth as teeth start to shift, and damage to the TMJ joint. Some people who suffer from bruxism are first diagnosed during routine dental visits when enamel destruction is noted.
Snap, crackle, pop
A number of studies have shown that TMJ dysfunction can exacerbate headache disorders, and that successful treatment of TMJ dysfunction can improve the headache disorder. As a headache specialist, I routinely evaluate the TMJ. During the examination, I palpate the joint, while the patient makes different jaw movements. I can often feel, and at times hear, the dysfunction in the joint. These problems are usually due to the misalignment or damage that has occurred to the tendons, ligaments, and/or cartilage involved with jaw movements. When severe, the TMJ can painfully "lock," and the person is unable to move their jaw until the joint is realigned, which can at times require surgery. These issues can occur in association with bruxism, excessive jaw clenching, jaw trauma, and at times without any clear cause.
My night…guard in shining armor
A very common treatment for TMJ dysfunction is the use of a nightguard, which is a plastic mouthpiece that covers the teeth, and prevents enamel on enamel contact. A nightguard is usually fitted to the upper (maxillary) teeth. In general, a dentist fabricates custom nightguards. Although usually more expensive, custom nightguards are a better choice than over-the-counter versions for a number of reasons. Custom night guards tend to be thinner and more comfortable. In addition, custom night guards are molded specifically to a person's teeth and bite. If a nightguard doesn't fit well, it can actually cause shifting of teeth and worsen TMJ symptoms. Although bruxism has never been a significant problem for me, I wear a nightguard to prevent enamel wear and shifting of teeth. After using a nightguard for a number of years, I tell patients that not wearing my nightguard is like not putting on my seatbelt after I get in the car. It is a disruption in my routine, which can at times leave me feeling restless.
Injecting conversation
Other treatments for TMJ dysfunction include injections directly into the joint and jaw surgery. One of the less invasive and less painful treatments is the use of botulinum toxin (Botox). Cosmetically, Botox works by relaxing the muscles that, when overactive, can cause wrinkles. Similarly, when injected into jaw muscles, they relieve tightness, pain, and wear on the TMJ. Two of my patients had very large jaw muscles from constant clenching over the years, and with Botox injections the contour of their faces changed. One of these patients said, "I hated having these big jowls. My jaw line is much smoother now, and my pain is essentially gone." Regarding side effects, another one of my patients asked, "Dr. Mathew, does injecting Botox in the jaw muscles cause any side effects?" I advised her, "Injecting too much Botox can cause jaw weakness when chewing something tough like steak, which can be a good thing." She responded, "How can jaw weakness be a good thing?" I replied, "If you are experiencing jaw weakness, it will be difficult for you to complain about me."
About the Author
Paul G. Mathew, MD, FAAN, FAHS, Contributor
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