If you are a nocturnal or sleep bruxer, your upper and lower teeth come clench together forcefully during the night — with a pressure of up to 700 pounds per square inch. (Normal daytime pressure, if you were to clench your teeth right now while reading this article, would be 200 pounds per square inch.)
There are two forms of night bruxism: clenching and grinding.
- If you clench your jaw without moving it around, the jaw remains clamped together forcefully for a sustained length of time.
- If you grind, your lower jaw moves side-to-side while clenched, making a distinctly unpleasant squeaking sound that can send your sleep partner running from the room.
All bruxism is classified as a parafunctional behavior, meaning it's a movement of the body that serves no purpose. Nocturnal bruxism is considered a movement disorder, and it's quite often associated with other sleep disorders like obstructive apnea and restless leg syndrome.
However, if you grind your teeth at least 2 to 4 times per hour, your bruxism may be diagnosed as a sleep disorder in and of itself. (A sleep study would be required to verify this.)
Why do people grind or clench their teeth?
The simple answer is, we aren't sure. Nocturnal tooth-grinding is an unconscious activity and it serves no practical biological function. Most people who grind their teeth or clench their jaws in their sleep aren't aware they're doing it.
Previously, experts speculated that tooth grinding might have been caused by infections or mechanical issues in the mouth, such as blockages or poorly-fitting dental prostheses. However, this is no longer thought to be the case.
More recently, research points to origins in the central nervous system. We still don't know the precise mechanism that triggers bruxism, but researchers have theorized that for some people, it may be an inherited genetic condition. For others, stress may play a role. Studies have shown that people (children included) who grind their teeth are also more sensitive to stress and hostility and more likely to have depression.
Bruxism is extremely common, affecting nearly one in eight people, mostly children and adolescents. Adults who experience bruxism are likely to have first experienced it as a child, and they may find that the condition ebbs and flows as they go through life. During some more stressful periods of their lives, for example, they may be more likely to brux.
Bruxism: symptoms & side effects
Bruxism isn't always easy to detect immediately. In many cases, people with bed partners are more likely to become aware they have the disorder; the sound of teeth rubbing against each other in the night wakes up their partners.
If you share your bed with someone, ask him or her if they can hear your teeth gnashing when you sleep. Many bed partners complain that the sound of grinding (or even squeaking!) teeth can wake them up or keep them from falling asleep.
However, there are some more subtle symptoms that can indicate you're a bruxer. These can include:
- Jaw or face pain or soreness. You may wake up in the morning with pain or tenderness in your jaw or your face. Jaw muscles can be tight or fatigued, as if you've been eating something tough and chewy.
- Lock jaw. In extreme cases, people with severe bruxism may have trouble opening or closing their jaws fully.
- Larger-than-normal jaw muscles. Very active chewers may develop masticatory muscle hypertrophy, a condition where jaw muscles become bulky from overuse. (As with lifting weights, the worked muscles put on bulk.)
- TMJ (temporomandibular joint) syndrome. Bruxism is a common cause of this sometimes painful condition, in which the hinge of the jaw becomes irritated from overuse. Symptoms of TMJ can include pain in the ear, face, and temples, a clicking sound when opening the mouth, earaches, hearing problems, ringing in the ears (tinnitus), neck pain, swelling, and lock jaw.
- Earaches. Pain that feels like an earache may actually have its origins in the temporomandibular joint (TMJ) of the jaw.
- Headaches. Bruxers may experience a dull headache that starts in the temples.
- Cracked or worn teeth. Teeth may be flat, have worn enamel, or show chips or fractures. Teeth may even be loose in the sockets. In the case of long-term bruxers, teeth can be worn down to stumps. People with bruxism may make more frequent trips to the dentist than non-bruxers for problems like cavities.
- Tooth sensitivity. Grinding down of your teeth and enamel can expose more of the root and nerve, which may lead to a greater sensitivity to heat and cold.
- Damaged fillings. Many people with bruxism will find that their fillings grind down and eventually disintegrate. If this happens, you may feel discomfort and sensitivity in your teeth. You may need to get new fillings or more serious dental work like a root canal.
- Bites on the inside of your cheek or tongue. Frequent clenching and grinding can lead to cuts or raised lines on the linings of your cheeks. You may also find bite marks or indentations on your tongue.
Tooth grinding, TMJD, and apnea: how they affect your sleep
For many people, these three conditions overlap.
- People with bruxism often develop TMJ problems; the pressure put on the jaw can lead to pain, inflammation, and related side effects like hearing problems. TMJ is a widespread issue; according to the National Institute of Dental and CranioFacial Research, about 44 million Americans have some form of TMJ disorder.
- People with TMJ disorder often report the classic symptom of grinding or clenching in the night.
- People with obstructive sleep apnea sometimes have underlying TMJ issues that cause the apnea. If the jaw and teeth are misaligned, the position of the tongue may block the airway, which can cause snoringand nighttime awakenings. Also, if you have obstructive sleep apnea caused by TMJ disorder, chances are you may be grinding or clenching as well. (Congratulations! You have all three.)
Together or individually, bruxism, TMJD, and obstructive sleep apnea can wreck your sleep by causing nighttime awakenings due to cessation of breathing (classic obstructive apnea events) or night headaches that mimic migraines.
How a sleep apnea mouthpiece can help
The most common treatment for sleep bruxism is to wear an acrylic mouth guard custom-fitted to your teeth. This mouth piece won't stop the actual grinding and clenching (and, therefore, won't stop headaches), but it does provide a protective barrier to prevent you from wearing away at your enamel or chipping your teeth. Generic mouth guards can be purchased in drugstores or you can visit your dentist to have a custom set made.
However, if you have been diagnosed with obstructive sleep apnea in addition to bruxism, a special sleep apnea mouth piece can be a good option for preventing some of the damage from grinding. These mouth guards — sometimes called mandibular advancement splints, or MAS — shift the position of your lower jaw to prevent airway obstructions and snoring.
Because they cover the upper and lower teeth and prevent direct contact, they may offer a similar level of protection from tooth grinding that you'd get from an acrylic mouth guard. But as an added bonus, they may also help to prevent the airway obstructions that could be waking you up multiple times per hour.
What to do if you think you're a grinder
If you have some of the bruxism or TMJD symptoms listed above but you're sleeping fine and feel rested, you may only need a trip to the dentist to get fitted for a mouth guard.
However, if you have the symptoms of bruxism combined with classic apnea side effects like daytime sleepiness, sore throat, brain fog, and concentration problems, you may want to visit a sleep specialist about doing a sleep study.