Newly discovered microbe keeps teeth healthy

What’s the best way to keep teeth healthy? The answer is simple. Regular brushing and flossing along with a diet low in sugary sweets and drinks. But the mouth also works to protect itself. In fact, some bacteria can halt or limit the tooth erosion that leads to decay, a new study finds. These germs naturally live in and around teeth. But not everyone’s pearly whites host a lot of these beneficial bacteria. Some scientists would now like to change that.

Their goal is to seed the mouth with these good bacteria. Such treatments are known as probiotics (Pro-by-OT-iks).

Marcelle Nascimento and Robert Burne are dental researchers at the University of Florida in Gainesville. They went scouting for a microbe to serve as a probiotic for teeth. To find it, their team used cotton swabs to sample bacteria in the mouths of kids ages 2 to 7 years old.

Cavities — also known as dental caries — are small holes that form in teeth. Some of these children had no cavities. Others had many.

The researchers tested different bacteria, looking for ones that could help fight tooth decay. The most promising germ came from a child with healthy teeth. Called A12, the microbe “has all the properties we look for in a bacterium to be able to fight caries,” says Nascimento.

A report of her team’s findings appears in the April Applied and Environmental Microbiology.

Acid warfare

Tooth decay can develop when too much acid builds up in the mouth. That acid will eat away at the hard outer coating, or enamel, that protects teeth. Acidic foods, such as lemons, limes and oranges can deliver some of that acid. But most of it comes from a bacterium known as Streptococcus mutans (STREP-tow-KOK-us MU-tans).

If A12 is a dental Superman, then S. mutans is Lex Luthor — a tooth’s archenemy. S. mutans munches on sugar, making lactic acid. The more sugar someone eats, the more S. mutans will flourish. And the more of these germs that colonize our teeth, the more lactic acid they can make.

Helpful bacteria tend to perish in a very acidic environment. So S. mutans can eventually take over the mouth. This can lead to cavities or more serious types of oral disease.

A12, though, has three special abilities that help it defeat S. mutans in the battle for healthy teeth. First, it makes a chemical weapon that kills S. mutans. The weapon is hydrogen peroxide. Many people use this substance on cuts or scrapes because it kills harmful bacteria. It has the same effect inside the mouth.

Second, A12 makes it hard for S. mutans to form biofilms. A biofilm is a community of microbes that sticks to a surface. In the mouth, biofilms include the white goopy stuff, called plaque, that builds up on teeth when someone forgets to brush. In order to settle into a biofilm, bacteria need to send and receive chemical messages. A12 interrupts these messages, leaving S. mutans bacteria unable to communicate.

Finally, and most importantly, A12 makes the mouth less acidic. It does this by making ammonia. And this “neutralizes acids that could destroy the teeth,” explains Nascimento.

Not ready for prime time

Don’t expect a dentist to send you home with some A12 after your next visit. “It’s still a really early discovery,” explains R. Dwayne Lunsford. He directs the microbiology program at the National Institute of Dental and Craniofacial Research in Bethesda, Md. This agency helped pay for the new study.

Probiotics for dental health will eventually become common, Lunsford expects. Most likely, helpful bacteria will be added to products that people already use, such as chewing gum, toothpaste or mouthwash, he says. The trick will be making sure that the bacteria stay alive in something like a strange, gum-wrapper home until they’re invited into someone’s mouth. And once they are, they will then need to successfully set up camp in a new mouth and survive long enough to make a difference in the fight against acid and S. mutans. That’s a lot to ask of these tiny germs.

Only time will tell if A12 is up to the task. In the meantime, Lunsford says, “There’s no substitute for brushing twice a day and flossing.”

Power Words

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acid     A chemical that releases hydrogen ions when dissolved in a solution. Acids have a sour taste and have a pH ranking of less than 7.0.

acidic     An adjective for materials that contain acid. These materials often are capable of eating away at some minerals such as carbonate, or preventing their formation in the first place.

ammonia     A colorless gas with a nasty smell. Ammonia is a compound made from the elements nitrogen and hydrogen. It is used to make food and applied to farm fields as a fertilizer. Secreted by the kidneys, ammonia gives urine its characteristic odor. The chemical also occurs in the atmosphere and throughout the universe.        

bacterium       (plural  bacteria) A single-celled organism. These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals.

biofilm     A gooey community of different types of microbes that essentially glues itself to some solid surface. Living in a biofilm is one way microbes protect themselves from stressful agents (such as poisons) in their environment.

caries     (in dentistry) A tiny hole in a tooth that develops over time. Also known as cavities, dental caries are more likely to happen when a person eats a lot of sugar or does not brush and floss teeth after every meal.

chemical     A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H₂O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.

dental     Pertaining to the teeth.

enamel    The glossy, hard substance that covers a tooth.

environment    The sum of all of the things that exist around some organism or the process and the condition those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.

germ     Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

hydrogen peroxide     A molecule made of two hydrogen and two oxygen atoms. Highly reactive, it can kill many tiny organisms, including germs.

lactic acid     A chemical compound commonly found in milk and in exercising muscles. Some bacteria in the mouth process sugar into lactic acid, which then promotes tooth decay.

microbe      Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

microbiology     The study of microorganisms, principally bacteria, fungi and viruses. Scientists who study microbes and the infections they can cause or ways that they can interact with their environment are known as microbiologists.

oral     An adjective that refers to things in or affecting  the mouth.

plaque   A biofilm, or community of bacterial species, that grows on teeth and other surfaces in the mouth.

probiotic    A beneficial bacterium that is found in food or can be added to the diet. It can fight bad germs in the body or perform functions, such as producing vitamins, that support human health.

Streptococcus mutans     A bacterium commonly found in the human mouth. Its growth may lead to tooth decay. The name is abbreviated as S. mutans.