Why do my dentures cause bad breath?

• Plaque on the denture. Dentures collect plaque and food just like natural teeth. Left uncleaned, the surface can harbor bacteria and yeast.
• Wearing them overnight. The NHS advises removing dentures every night; leaving them in raises the risk of gum infections and decay in any remaining teeth.
• An uncleaned tongue. Without natural teeth, many people stop cleaning their mouth itself, and the tongue coats over.
• Loose or ill-fitting dentures that trap food underneath.
• Denture stomatitis, a yeast infection under the denture, covered below.
• Dry mouth, which is common in older adults and often linked to medicines.

A 2022 study followed people getting new complete dentures. About two-thirds had bad breath at follow-up visits. Bad breath was much less common in people who brushed their tongue than in those who did not, and it was more common in people who slept in their dentures or had a heavy tongue coating. Not cleaning the tongue was the only factor linked to bad breath at both follow-ups, with about a 16-fold higher likelihood.

As for which denture cleaning method is best, a Cochrane review found that chemical cleansers and brushing both reduce plaque and bacteria on dentures compared with no treatment, but there is not enough good evidence to say one method beats another.

1. Rinse your dentures after meals to remove loose food.
2. Brush your dentures every day with a soft brush and a non-abrasive denture cleanser. The NHS advises not using regular toothpaste, which can scratch them.
3. Take them out at night and keep them in water or an overnight denture-cleaning solution, as the NHS and MouthHealthy recommend.
4. Clean your mouth every morning before putting dentures in: brush your gums, tongue, roof of your mouth and any remaining teeth with a soft brush, as MouthHealthy advises.
5. Clean your tongue daily with a brush or scraper; this was the biggest factor in the study above.
6. Keep checkups even with full dentures, so your dentist can check the fit and your gums.

Tongue cleaning makes sense for denture wearers because the tongue is a large surface for bacteria and the denture study above found it mattered most. It is fair to say the wider evidence is limited, though: a 2019 Cochrane review of treatments for bad breath found only two small trials of tongue cleaning (46 people in total) and rated the evidence as very low certainty. Tongue cleaning is cheap and low risk, so it is a reasonable habit, but it is one part of a routine that also includes cleaning the denture and taking it out at night.

Denture stomatitis is a yeast infection, a type of thrush, in the tissues under a denture. Cleveland Clinic cites research suggesting it affects up to 67% of denture wearers, more often those with full dentures. Risk factors include wearing dentures overnight or for long periods, poor hygiene, a sugary diet, smoking or vaping, broad-spectrum antibiotics and a weakened immune system.

Signs include redness or white or red patches under the denture, soreness, and cracks at the corners of the mouth. It needs a dentist or doctor, who may prescribe antifungal treatment and check the denture fit; Cleveland Clinic says most people improve within two weeks of starting treatment.

The NHS advises seeing a dentist if your dentures are loose or uncomfortable, damaged, or if you have very red or bleeding gums or bad breath, which can be signs of gum disease, a fungal infection or tooth decay. Sores that do not heal under a denture should always be checked.