Teeth clenching and/or grinding during sleep (a phenomenon known as “bruxism”) is a common problem. Some people are aware they do this because they wake up with headaches, jaw pain, lock jaw, or temporomandibular joint (TMJ) pain. Others know about it because their bed partners hear them making grinding noises with their teeth during the night. Still others discover it because their dentists (or sleep doctors) note it. The common treatment for this in dental medicine is to wear a bite guard. These dental devices create a buffer zone between the upper and lower teeth to protect against enamel wear and reduce the strain on the TMJ.

Unfortunately, bite guards do not treat the underlying condition. Traditionally, patients have been told their bruxism is a byproduct of stress, a response mechanism to waking during the night, or that the cause is unknown. As I wrote in 2013 for the Huffington Post, we now understand the reason why many patients suffer from this condition: it is due to changes in airflow during sleep.

Sounds far fetched? Let me explain the physiology. When we fall asleep, the cerebral cortex (that’s the highly folded outer part of our brain that makes us so much smarter than other living creatures) goes into a hibernation of sorts. This leads to deregulation of body functions that are well managed when we are awake. For instance, our conscious awareness and memory formation is halted (unless we wake up). One other thing that happens is our muscles relax. Just picture me (the sleep doc) sitting on a stool in the office while talking to a patient. Now picture me asleep on the same stool, and try to imagine how long it will take for me to fall off of it. You would guess correctly that it would occur very quickly. Why? My muscles would relax when I fell asleep, and I’d no longer be able to maintain the posture of sitting upright without any support.

The airflow from the nose and mouth meets in the back of the throat before going into the trachea (“the windpipe”). The image on the left shows a normal airway during sleep, while the one on the right shows a collapsed airway during sleep.

Now let’s talk about how that example relates to bruxism. Just like the muscles needed to stay perched on a stool relax when we fall asleep, so too do the muscles of the jaw, the tongue muscles, and the muscles of the throat. The result is that our jaw slides back, dragging the tongue in tow with it. (The tongue base is attached to the jaw.) This makes the size of our airway smaller during sleep. This is true of 100% of people. For some people, this is no big deal because they have enough reserve space in the back of the throat. For others, it makes the work of breathing harder, perhaps even leading to a collapse of the airway and pauses in breathing. If this narrowing is significant enough to cause partial or complete closing of the airway, one way to gain temporary relief is to thrust the jaw forward. This forward thrusting leads to widening of the airway by moving the tongue away from the back of the throat. It just so happens to also scrape the teeth, which of course is teeth grinding. If this behavior is successful, the body may repeat the behavior, perhaps also locking the jaw place, which is teeth clenching.

This is more than just a theory. In 2009, my colleague Jerald Simmons, M.D. and our dental colleague Ronald Prehn, D.D.S. demonstrated this conclusively. They found that patients complaining of bruxism and Obstructive Sleep Apnea (OSA) almost all had improvement of their bruxism with CPAP therapy alone, with more than half of patients reporting complete resolution. This striking result solidified the understanding of these interrelated issues.

So while the relationship between a dental condition and a potentially serious medical condition may not be intuitive at first, it is important to recognize this important connection. Untreated OSA is potentially fatal. For those patients whose OSA is less severe (such as in the Upper Airway Resistance Syndrome), treatment can still improve quality of life significantly, as well as save a patient thousands of dollars in dental work!