Feb. 20, 2002 -- Dental care could soon involve a process as simple as this: Rinse once, feed bacteria.

A Florida researcher is hoping to soon begin clinical trials for his bacterial rinse that's designed to stave off tooth decay for a person's lifetime. So far, the rinse has worked in rats and early prototypes have been tested in three people.

"You would just need to squirt onto tooth surfaces once," said Jeffrey Hillman a professor of oral biology at the University of Florida in Gainesville.

Bacteria, he explains, take care of the rest.

The rinse could be a wonderfully simple approach to dental care, although some worry that introducing a modified microbe directly into the body could lead to trouble.

Building a Bug Weapon

Most tooth decay is caused by a particular strain of bacteria called Streptococcus mutans (S. mutans). While 500-600 different kinds of bacteria thrive on mucus and food remnants in the mouth, S. mutans is particularly damaging because it consumes sugar (mostly refined sugars) on the surface of teeth and converts it to lactic acid. The lactic acid is what eats away at a tooth's enamel.

In the early 1980s, Hillman set out to find a bacterium that might destroy the decay-causing strain. After taking hundreds of sample swabs from patients' mouths, he found a bacterium that secretes a toxin that kills S. mutans.

Hillman and his colleagues then altered a gene in the bacterium so it would not secrete lactic acid of its own. Recently they tweaked the bacterium again so it would only survive if fed a particular nutritional supplement. That ensures the bacterium won't spread from one person to another while kissing or sharing utensils.

"Subjects will have to chew gum or use mouthwash to provide the bacteria with its nutritional supplement," said Hillman.

When Hillman squirted the strain on rats, the substance appeared to prevent tooth decay in the animals for the entire six-month period of the tests. He has also squirted a version of the bacterium on three human volunteers.

The strain these people harbor in their mouths kills off the S. mutans bacterium, but does not prevent decay since it also produces lactic acid. Tests show the strain has successfully warded off all S. mutans bacteria since the early 1980s. And none of the three subjects have passed on their unique mouth bacteria to their spouses or children.

Ecosystem in Your Mouth

Some might worry that releasing a genetically altered creature inside the human body could lead to trouble. But Hillman claims he's just speeding up evolution. The decay-causing bacterium was probably innocuous until people began eating large quantities of refined sugar. Another 1,000 years and people might have shed the S. mutans bacterium anyway, he says.

Other dental experts warn it can be dangerous tinkering with the body's complex balance of bacteria.

"There are many varieties of bacteria in the mouth and they live in a kind of ecosystem there," said Kenneth Burrell, senior director of the American Dental Association's Council on Scientific Affairs. "There's a balance there if you upset it, you can throw off the bacterial population. And some bacteria may be necessary to maintain a healthy mouth."

Burrell adds, however, if tests show the rinse does not upset this balance it could be a boon to dental hygiene. The rinse would only need to be applied once — preferably when a person is very young — and then the bacterium would settle into the patient's mouth for life. Adult patients could also use the rinse to prevent any further dental decay they may have already experienced.

Bacteria is often thought of as a target when it comes to cleaning, but recently, researchers have found strains that work well as cleaning tools. Companies like BioOne and Eco-Save provide cleaners that employ bacteria to eat through plumbing and bathroom scum. And environmentalists have found certain bacteria are effective in cleaning up toxic waste.

Now Hillman's bacterial strain, known as BCS3-L1, could take up a similar role in the mouth. Hillman presented his findings at this year's meeting of the American Association for the Advancement of Science in Boston.

Fewer Trips to the Dentist?

Just because a bacterium may be fighting tooth decay in your mouth doesn't mean you'll be free of the task of tooth brushing and flossing, Hillman says. Those daily practices are still needed for preventing gum disease and bad breath.

And while the thought of a decay-ending agent may cause unease among some dentists who make a living on the problem, Burrell points out the rinse could actually end up improving business.

"If this rinse really works, it could mean the average person will have their teeth for a longer time," he said. "Then they might have various gum infections that they wouldn't have experienced if they lost their teeth to tooth decay, and they'll need dentists for that."