50% of dental retainers harbour microbes

Germs can often lurk in the most unlikely places; now experts have found potentially harmful microbes on half of dental retainers.

Researchers at the Eastman Dental Institute in London sampled the mouths of people who wore the two most widely used types of dental retainers and compared them with those from people without the devices.

Retainers are often worn after dental braces to hold the newly aligned teeth in position. But as they are frequently removed and replaced in the mouth, the potential for contamination with microbes is high, said Dr Jonathan Pratten, who led the study.

Mouths are full of different types of bacteria, some of which are good for oral health. However, the researchers looked for microbes not normally found in the mouth.

Candida, a type of yeast, was detected on 67 per cent of retainers. The bacterium staphylococcus - including antibiotic resistant MRSA - was found on 50 per cent of retainers tested.

Both microbes were also present inside the cheeks and on the tongue of retainer wearers.

The bacteria on the retainers live in biofilms, clusters of microbes living together in a layer of slime. Biofilms can be difficult to remove and are often more resistant to treatment by antibiotics.

Although Candida and Staphylococcus rarely cause problems in healthy individuals, they can cause problems in people with weakened immune systems, said the researchers.

"With the growing awareness the public has of hospital-acquired infections it is important to be aware of other potential 'hidden reservoirs' of harmful bacteria which could be introduced to environments where we know they can cause problems," Dr Pratten said.

He said that good hygiene was key to reducing contamination of retainers with these microbes. Anyone handling a retainer should wash their hands before and after use. Careful tooth brushing and mouthwash may also help to keep the retainer clean.

The findings are reported in the journal Letters in Applied Microbiology.

This article was published on Wed 16 March 2011