Medically reviewed by Brittany Ferri, PhD
Teeth grinding or gnashing and jaw clenching during sleep, also known as sleep bruxism, might seem like mere nuisances. However, these phenomena are deeply rooted in our sleep physiology and might serve a purpose beyond mere habit. Let’s explore the fascinating science behind why our bodies engage in this seemingly peculiar activity.
The Science Behind Teeth Grinding
Sleep is a complex process involving the coordination of autonomic processes that keep our bodies functioning while we are unconscious. It’s like a ballet, but instead of dancers, it’s the various parts of your body moving in harmony while you sleep. One surprising performer in this nighttime ballet is sleep bruxism, commonly known as teeth grinding and jaw clenching. But before you dismiss this as just a bad habit, let’s dive into the fascinating science behind why our bodies engage in this seemingly peculiar activity.
At the heart of sleep bruxism is a phenomenon called Rhythmic Masticatory Muscle Activity (RMMA). Unlike the deliberate act of chewing, RMMA doesn’t involve the brain’s conscious movement centres. Instead, it’s more like an automatic reflex, controlled deep in the brain’s sleep centres. While chewing involves alternating contractions of jaw muscles, RMMA involves simultaneous contractions of these muscles.
The term “rhythmic” means these episodes happen in clusters during sleep, typically linked with brief awakenings or sleep arousals—those moments when sleep is momentarily interrupted. These arousals come with increased heart rate, blood pressure, and breathing rate, providing clues to their origin.
Contrary to the perception of teeth grinding as abnormal, research shows it is actually common. One study found that 60% of people show some level of RMMA during sleep. This discovery has led scientists to question whether or not RMMA is a natural part of our sleep physiology, and if sleep bruxism is simply a more intense version of a normal jaw movement during sleep.
Wait, what?
Yes, the jaw movement we associate with teeth grinding and clenching might actually have a useful function. Experts no longer label sleep bruxism as a disorder, but as a behaviour, suggesting it may be a natural or adaptive response rather than an abnormality.
Understanding Sleep Bruxism
This new understanding of sleep bruxism challenges its clinical implications.
First, decades of research have shown that sleep bruxism is primarily driven by our central nervous system, not by dental concerns like how your teeth fit together. A review of over 40 studies found no evidence linking dental bite issues to sleep bruxism. Notably, in a detailed sleep study, researchers looked at 26 different aspects of participants’ bite characteristics and 25 measurements of their head and jaw shape, comparing people who grind their teeth with those who don’t. They didn’t find any differences between the two groups. Simply put: not everyone who grinds their teeth has misaligned teeth, and not everyone with misaligned teeth grinds their teeth.
Secondly, sleep bruxism has traditionally been seen as a concern that needs fixing. But what if it’s actually an adaptive feature of our physiology, helping our bodies deal with disturbances that occur each night?
This perspective doesn’t minimise the real discomfort and dental concerns bruxism can cause. Rather, such an approach shifts the focus of sleep bruxism treatment towards understanding and managing the underlying triggers rather than eliminating the grinding behaviour entirely. Factors like sleep disorders, routines, stress, anxiety, and overall sleep hygiene (including your sleep environment and habits surrounding sleep) should be addressed to reduce microarousals or overactivation of the sympathetic nervous system during sleep. This could lead to more holistic and sustainable management strategies.
Conclusion
Rather than viewing sleep bruxism as a disorder, it might be more useful to see it as an intensification of normal behaviour, influenced by disruptions in the sleep process and the autonomic nervous system. So, next time you think about the enigma of sleep bruxism, picture it not just as an annoying interloper in the night, but as part of a complex, adaptive system that helps maintain the restorative sleep our bodies need. It’s a reminder of the incredible, often unseen work our bodies do every night to keep us running smoothly.
By addressing the root causes of sleep disturbances—from stress management to addressing sleep apnea—we can help this nighttime ballet choreograph a more harmonious routine, ensuring that every part of our body, including teeth and jaw muscles, gets the rest it deserves.
