Biting the inside of your cheek during sleep is almost always caused by teeth grinding (bruxism), a misaligned bite, or both. Because you’re unconscious when it happens, the fix involves addressing the root cause and physically preventing your teeth from reaching your cheek tissue. The good news: most people can stop the damage with the right mouthguard and a few targeted changes.
Why It Happens While You Sleep
During sleep, your jaw muscles can clench and grind with surprising force, and your cheek tissue gets caught between the upper and lower teeth. Johns Hopkins Medicine lists damage to the inside of the cheek as a direct symptom of bruxism. About one-third of people with obstructive sleep apnea also grind their teeth at night, meaning disrupted breathing can trigger the jaw activity that leads to cheek biting. If you snore heavily or wake up feeling unrested, sleep apnea could be an underlying factor worth investigating.
Bite alignment plays a major role too. A crossbite (where upper teeth sit inside the lower teeth) or an overbite pushes cheek tissue closer to the grinding surfaces of your molars. Cleveland Clinic specifically lists cheek biting as a symptom of malocclusion. Even a single misaligned tooth can create a spot where soft tissue gets pinched repeatedly in the same place, night after night.
The Role of Stress and Nutrition
Stress is the most common trigger for sleep bruxism. When your nervous system stays activated at bedtime, your jaw muscles are more likely to clench involuntarily. But nutritional gaps can make the problem worse in ways most people don’t realize. Low levels of vitamin D, magnesium, and omega-3 fatty acids all increase what researchers call neuromuscular excitability, essentially making your muscles more twitchy and prone to involuntary contraction.
Magnesium deficiency is particularly relevant. It causes muscle irritability, anxiety, and insomnia, all of which feed into nighttime grinding. Low vitamin D disrupts calcium balance, which directly affects how your muscles contract and can trigger spasms. If you’re grinding and biting your cheeks at night, these deficiencies won’t be the sole cause, but correcting them can reduce how intensely your jaw muscles fire during sleep.
Why a Mouthguard Is the First Line of Defense
A mouthguard (also called a bite splint or night guard) creates a physical barrier between your upper and lower teeth, preventing them from trapping cheek tissue. This is the single most effective way to stop the tissue damage while you work on the underlying causes.
Custom-fitted guards from a dentist are significantly better than over-the-counter versions. In a randomized controlled trial comparing the two, 90% of the store-bought guards had critical fabrication errors when users tried to mold them at home, and only 4 out of 31 were clinically acceptable. People using the OTC guards also had significantly more grinding bursts per hour (about 31 per hour versus 19 for the custom-fitted group). Both types held up similarly in terms of material wear and gum health over four months, but the custom guard did a meaningfully better job of reducing grinding activity.
If cost is a barrier, an OTC boil-and-bite guard is better than nothing. Just know that the fit will likely be imperfect, which means less protection for your cheeks. Many dental offices now offer payment plans for custom guards, which typically range from a few hundred to over a thousand dollars depending on the type.
Behavioral and Lifestyle Changes That Help
Biofeedback therapy has shown the strongest results among non-device approaches. In clinical studies, biofeedback reduced jaw muscle activity during sleep by 52 to 55% compared to baseline. One system uses a pressure sensor inside a mouth splint that sends a signal to a wristwatch vibrator when it detects excessive clenching. In a 12-week study, both the frequency and duration of grinding episodes dropped significantly in the vibration group, while the control group saw no change.
Relaxation techniques and sleep hygiene on their own are less impressive. One trial combining sleep hygiene education with muscle relaxation exercises found no significant reduction in grinding episodes after four weeks. That doesn’t mean relaxation is useless. It just means it works better as part of a larger strategy rather than a standalone fix. Reducing caffeine and alcohol in the evening, keeping a consistent sleep schedule, and practicing progressive muscle relaxation (deliberately tensing and releasing your jaw, neck, and shoulder muscles before bed) all lower the baseline tension your jaw carries into sleep.
Fixing the Bite Itself
If your cheek biting stems from misalignment, a mouthguard manages the symptom but doesn’t solve the structural problem. A dentist or orthodontist can evaluate whether a crossbite, overbite, or individual tooth position is creating a “trap” for your cheek tissue. Orthodontic correction (braces or clear aligners) repositions the teeth so the cheek no longer falls into the bite path. In some cases, smoothing or reshaping a single sharp or protruding tooth is enough to eliminate the problem.
Dental work like crowns, fillings, or implants that changed your bite profile can also introduce new cheek-biting patterns. If the problem started after a dental procedure, mention the timing to your dentist, as a simple adjustment may fix it.
What Happens If You Don’t Address It
Occasional cheek biting heals on its own within a few days. Chronic, repeated biting is a different story. The tissue develops a rough, shredded texture (sometimes whitish from constant irritation), and open sores can develop. In some people, the habit becomes self-reinforcing: the swollen, damaged tissue sticks out further, making it easier to bite again the next night.
There’s also a longer-term concern worth knowing about. Chronic mechanical irritation of the oral mucosa has been studied as a potential contributor to oral cancer. The research suggests that repeated tissue trauma alone probably can’t cause cancer, but it can accelerate the process if other risk factors are present (like tobacco use or alcohol). In studies of chronic irritation linked to oral cancer, the average duration of irritation was about four years. The buccal mucosa (inner cheek) was the most commonly affected site, involved in 45% of cases. This isn’t a reason to panic, but it is a reason to take chronic cheek biting seriously rather than ignoring it indefinitely.
A Practical Plan to Start Tonight
The fastest path to relief combines immediate protection with longer-term fixes. Start by scheduling a dental appointment to evaluate your bite and get fitted for a custom night guard. In the meantime, an OTC guard offers some protection. Address the controllable factors: reduce evening stress and stimulants, check whether you’re getting adequate magnesium and vitamin D (a simple blood test can confirm), and pay attention to whether you’re also clenching during the day, since daytime clenching often predicts nighttime grinding.
If you wake up with jaw soreness, headaches, or notice scalloped edges on your tongue alongside the cheek damage, those are strong signs of bruxism. If you also snore or feel excessively tired during the day, bring up the possibility of sleep apnea, since treating the breathing disorder often reduces the grinding that causes cheek biting.