CPAP dry mouth: why it happens and how to protect your teeth

What’s going on

CPAP Strong keeps your airway open with a steady flow of air. That air is drier than your own breath. If some of it escapes through your mouth all night, your mouth dries out.

Dry mouth is one of the most common CPAP complaints. In a French study of 1,484 long-term CPAP users, leak-related problems were the most common mask side effects. People who reported a dry mouth were more likely to use CPAP less than four hours a night.

So a dry mouth isn’t just uncomfortable. It can make you give up on a treatment that works.

The usual causes

• Mouth leak. You wear a nasal mask or nasal pillows, but your mouth falls open during sleep. Air flows in through your nose and straight out of your mouth.
• Mask type or fit. A mask that doesn’t suit how you breathe, or doesn’t seal well, lets air escape.
• Low humidity. The heated humidifier is off, empty or set too low.
• A blocked nose. When your nose is stuffy, you breathe through your mouth, with or without CPAP.

Medicines can dry your mouth too. The ADA lists antihistamines, decongestants and many others. The ADA also notes that mouth breathing makes dry mouth worse.

What helps

These are fixes to talk over with your sleep physician or equipment supplier. Don’t change your pressure settings on your own.

Heated humidification

AASM’s troubleshooting guide says most CPAP machines include a heated humidifier. Turning it on, or raising the setting, may help a dry mouth, nose or throat.

The research is thin. A 2019 Cochrane review found too little evidence to say how much humidification changes comfort or nightly use. If you get water in your tubing (“rainout”), AASM suggests a heated tube or tubing wrap.

A mask that covers your mouth

If you breathe through your mouth at night, AASM suggests considering a full-face mask that covers your mouth and nose. It’s also an option when your nose is often blocked.

A full-face mask can leak in new places, especially if you sleep on your side. See CPAP masks for side sleepers for fit and pillow tips.

A chin strap, with CPAP only

If you wear a nasal mask or nasal pillows, AASM says a separate chin strap may help keep your mouth closed and reduce the leak. It’s a CPAP accessory.

A chin strap on its own doesn’t treat sleep apnea. Don’t use one in place of CPAP.

A clearer nose

AASM suggests more humidification for a stuffy nose. It also lists prescription nasal sprays, and an ear, nose and throat specialist if the congestion lasts. Ask your physician which fits you.

What dry mouth does to your teeth

Saliva protects your teeth. NIDCR says it washes food away and carries calcium and phosphate, minerals that help teeth fight decay.

When your mouth stays dry, that protection drops:

• Cavities. NIDCR and the ADA both say dry mouth raises the risk of tooth decay. The ADA notes decay near the gumline and on the tips of teeth.
• Gum problems. The ADA lists plaque buildup, gingivitis and periodontitis. Cleveland Clinic lists gum disease among the complications.
• Mouth infections. NIDCR and Cleveland Clinic both mention fungal infections such as thrush.

Eight hours a night of dry air adds up. That’s why a CPAP user with a dry mouth should mention it to a dentist, not only to the sleep team.

For more on how a dry mouth leads to decay, see dry mouth and cavities on our sister site.

Habits that protect your teeth

1. Brush with fluoride toothpaste twice a day. The ADA recommends it for everyone with dry mouth. Brush last thing before you put your mask on.
2. Ask your dentist about extra fluoride. For people with dry mouth, the ADA lists prescription-strength fluoride gel and fluoride varnish applied at the dental office.
3. Keep water by the bed. NIDCR suggests drinking plenty of water. Plain water is the safest thing to sip at night.
4. Chew sugar-free gum during the day. NIDCR and the ADA both say sugar-free gum or candy helps saliva flow. NIDCR adds that some with xylitol may help prevent cavities.
5. Limit alcohol, tobacco and caffeine. NIDCR says they dry out the mouth.
6. Keep up with dental checkups. NIDCR recommends regular visits. Tell your dentist you use CPAP.

A room humidifier Weak at night is also on NIDCR’s list. It’s a comfort measure; it isn’t a substitute for the CPAP humidifier.

What a dentist or doctor can do

Your sleep physician or equipment supplier can check your machine’s leak data, review your mask and humidity settings, and switch your mask if needed.

Your dentist can look for early decay and gum changes, apply fluoride varnish, and prescribe a fluoride gel. A dentist can also check whether a medicine or another condition might be adding to the dryness.

If you still can’t settle with CPAP, talk to your physician about alternatives. A custom oral appliance Some is one option for people who can’t tolerate CPAP. See oral appliance vs CPAP.

What not to do

• Don’t stop CPAP because of dry mouth without telling your physician. Most causes have a fix.
• Don’t tape your mouth shut on your own. Mouth tape Weak + warning has weak evidence, and it’s risky if your nose blocks up. Ask your sleep team first.
• Don’t sip sugary drinks in the night. With little saliva to wash your teeth, the sugar stays put.
• Don’t wait for pain. Early decay and gum changes often don’t hurt. A checkup finds them sooner.