Medically reviewed by Brittany Ferri, PhD
The physiological benefits of sleep
You probably don’t spend much time thinking about sleep, seeing it as a necessary daily routine that happens outside your conscious control. With our consciousness suspended during sleep, it might seem like nothing happens at all.
But we all know sleep is vital for our physical and mental well-being. After a bad night’s sleep, we feel sluggish, tired, and achy. Our thinking slows down, and our mood worsens. These effects are real. Sleep allows our body to repair tissues, make proteins, and release hormones that control growth and appetite.
Our brains also benefit, as sleep helps us consolidate memories, clear out toxins, and reorganize neural networks. Sleep is crucial for cognitive function, emotion regulation, and overall health. Skipping sleep not only harms these functions but can also lead to serious health concerns like heart disease, obesity, diabetes, and a weakened immune system.
Sleep is a dynamic process
Far from being a quiet, inactive state, sleep is a dynamic process. While we are unconscious, our autonomic nervous system (ANS) keeps working. The ANS regulates involuntary functions like heart rate and breathing, keeping the body running smoothly without our conscious control. It has two main parts: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS).
The sympathetic nervous system is the “fight or flight” system, preparing the body for action in times of stress. The parasympathetic nervous system is the “rest and digest” system, helping the body relax and perform vital maintenance tasks like digestion and repair.
During sleep, the PNS generally takes over, promoting relaxation and recovery. This shift is essential for effective sleep, allowing the body to heal and regenerate. Heart rate and breathing slow down, muscles relax, and energy is conserved.
However, the SNS doesn’t shut down completely. It periodically activates to trigger brief wakefulness moments (“microarousals”) lasting 2-15 seconds. These keep us slightly alert to the environment and potential dangers, even while we are asleep. When the SNS activates, our heart rate might speed up, our muscles might tense, and our brain activity increases, although we remain asleep. This is an entirely normal process, built deep into our biological processes, to keep us safe.
Relationship Between Sleep Bruxism and the Nervous System
So how does this relate to teeth grinding? What is the relationship between brief awakenings, the balance of the SNS and PNS, and teeth grinding?
You might wonder why our bodies would choose to grind teeth during these times. It turns out this might be our body’s way of keeping sleep stable. Spikes in SNS activity can disrupt the restful part of sleep, which is controlled by the parasympathetic nervous system (PNS). Grinding or clenching during these jaw muscle movements might stimulate the trigeminal nerve, which controls facial sensations and movements like chewing. This stimulation could trigger the Trigeminal Cardiac Reflex (TCR), a protective response that shifts the body back to a restful state, reducing heart rate, breathing, and blood pressure, thus stabilising sleep.
This suggests that these jaw muscle movements and sleep bruxism might not be random acts but rather a sophisticated mechanism to maintain sleep quality. It’s like the body switching gears to return to a calm, restful state amidst potential sleep disruptions.
Multiple studies support this idea. For example, clonidine, a medication known to reduce SNS activity, has been shown to decrease the frequency of these jaw muscle movements in people with sleep bruxism. Other studies also show that these movements are often preceded by increased SNS activity and followed by increased PNS activity.
This indicates that jaw muscle movements act as a natural way for the body to regulate itself, helping it return to a state conducive to restful sleep, rather than being a disorder.
Conclusion
Sleep bruxism, or teeth grinding, is not just a random or abnormal act; it’s a complex and potentially normal behaviour deeply rooted in our sleep physiology. The balance between the sympathetic and parasympathetic nervous systems plays a crucial role in maintaining the stability and quality of our sleep. This balance is delicate, and disruptions can lead to teeth grinding as a way for the body to stabilise itself during sleep.
Understanding that grinding is a sophisticated mechanism rather than a disorder allows us to appreciate the intricate ways our bodies work to maintain restful sleep. By addressing factors that disrupt this balance, such as stress, sleep environment, and overall sleep hygiene, we can better manage sleep bruxism and improve our sleep quality and overall health. This insight reminds us of the remarkable, often unseen efforts our bodies make to keep us running smoothly, ensuring every part, including our teeth and jaw muscles, gets the rest it needs.
