A SINGLE dental treatment that involves spraying genetically-modified bacteria into a patient’s mouth could cut the risk of cavities by up to 90 per cent, according to new research. The spray, which could be on the market in as little as three years and should last a lifetime, contains bacteria similar to that found naturally in the mouth – with one crucial difference.

The natural bacteria, streptococcus mutans, produces lactic acid that eats away at teeth, causing decay, whereas the GM bacteria does not.

Planting the new form inside the mouth means the natural kind cannot get a foothold, so only one application would ever be needed.

The first human trials to check for safety have been carried out among people with dentures – so they could be removed at any sign of a dangerous reaction – proved successful and there are now plans to carry out tests on people with their own teeth.

Professor Jeffrey Hillman, of Florida University, the reseach team’s leader, said the anti-cavity spray had been shown to protect rats’ teeth, and he believed it will be as effective in humans.

“We think it will be dramatic, probably a 70, 80 or 90 per cent reduction, but it’s hard to say for certain,” he said.

“You have about 700 different types of bacteria in your mouth. We are just replacing a particular organism that causes tooth decay with one that doesn’t… You’ll still need to brush your teeth, you don’t want gum disease or bad breath.

“As a dentist myself, I would have trouble saying you could eliminate the need for brushing. You’ll be the same human being, you’ll just have a decreased likelihood of tooth decay.”

He is currently talking to the US Food and Drug Administration, which has been monitoring progress and insisted the first human trial were in people with dentures.

“I understand the FDA’s concern for safety and effect, but if you were to sit down and try to imagine what the worst possible outcome could be, it’s hard to think of anything,” said Prof Hillman, who was in Edinburgh this week for a Society for Applied Microbiology conference.

He said the treatment could become available in “three, four or probably five years”.

Dr Nigel Carter, chief executive of the British Dental Health Foundation, said it was great to see so many positive developments in science which could improve dental health. But it was vital that such discoveries did not become an excuse for people to accept poor dental hygiene.

“You need to take good care of your teeth and mouth on a daily basis,” Dr Carter said. “That means developing a good oral healthcare routine including twice-daily brushing with fluoride toothpaste, limiting the frequency of sugary foods and drinks and visiting the dentist as often as they recommend.

“A good oral healthcare routine really is the only surefire way of guarding against poor oral health.”