New pain-free treatments
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Special to msnbc.com
updated 10/15/2003 6:04:17 PM ET 2003-10-15T22:04:17

The next time you plant a big, wet juicy one on the lips of your significant other, think about this: In each of your very kissable mouths lives more than 500 species of bacteria. Billions and billions of them. They grow on every slimy surface, dark nook and inviting cranny. By understanding the complex relationships among the inhabitants of this tiny jungle ecosystem, researchers plan to usher in a new era of pain-free dentistry. No more drills. No more fillings.

In essence, each of us walks around with our own miniature rain forest that’s a perfect environment for bacteria. The mouth has an average temperature of 95 degrees Fahrenheit. Its humidity hovers at 100 percent. It’s stoked regularly with sugar and simple carbohydrates, manna from bacteria heaven.

In one mouth, the number of bacteria can easily exceed the numbers of people who live on the entire planet, according to Dr. Sigmund Socransky, a researcher who’s been studying these microscopic critters for decades at the Forsyth Institute in Boston.

In a recently brushed mouth, he said, 1,000 to 100,000 bacteria live on each tooth. In a dirty mouth, however, each tooth harbors 100 million to one billion bacteria. The good news is that most are friendly.

In exchange for living in this tropical paradise, the hundreds of species of beneficial bacteria help fend off disease-producing bacteria that attempt to invade the mouth from the outside world. It’s only about a dozen species of bacteria and yeast that can cause infections in the teeth and gums.

WAR ON CAVITIES

A new world of dental research has bloomed around oral ecology. Investigators are hoping to devise ways to spot cavities before a dentist can see them, induce teeth to repair themselves, make diseased gums grow healthy tissue, put antibodies to disease-causing bacteria into plants that we’d eat, and seal mothers’ teeth so that they don’t transmit cavity-causing bacteria to their babies.

The simple fact is that we’ve gone about as far as we can with brushing, flossing and adding cavity-fighting fluoride to water supplies, toothpaste and mouthwashes. Fifty-one percent of American kids under 12 don’t have cavities. But of the 49 percent that do, many have disease that’s difficult to control, even with the best dental hygiene. And gum disease, which is caused by about a half-dozen types of bacteria, plagues millions of adults.

In the last few years, researchers have made significant strides in understanding the bacteria better, and how they are transmitted from person to person. One important discovery was that a type of cavity-causing bacteria known as Streptococcus mutans comprises thousands of different strains, some that are more harmful than others, which partly explains why some people have more, or more severe, cavities than others.

A lab worker studies Streptococcus mutans, a type of bacteria that causes tooth decay.
At the University of Alabama School of Dentistry, Dr. Page Caufield, a professor of oral biology, found that humans are colonized by S. mutans during a “window of infectivity,” around two years of age. At that time, S. mutans is passed from the primary caregiver — usually the mother — probably through saliva transmitted when miniscule droplets are spewed by talking into the face of a child whose teeth are emerging. “The window opens and closes,” said Caufield. “If children aren’t infected by S. mutans then, another bacteria species colonizes and uses that niche. People don’t exchange S. mutans as adults.”

However, recent studies indicate that bacteria that cause gum disease are passed between spouses, said Dr. Ernest Newbrun, a dental researcher at the University of California San Francisco Medical Center. “It isn’t clear that that’s the only way those bacteria are transmitted, but it seems to require direct mouth-to-mouth contact, in other words, kissing.”

This knowledge is leading scientists to develop new methods of preventing diseases of the teeth and gums. “Instead of trying to kill all the microorganisms, we’re targeting specific interactions,” said Dr. Irwin Mandel, retired from decades of research at Columbia University School of Dental and Oral Surgery in New York. “It’s more of a magic-bullet approach than a shotgun approach.”

BEYOND THE MOUTH

Though oral ecology began as a search for new ways to treat cavities and gum disease, it has expanded into the whole body. “We look at how the oral microbes, which are generally harmless in the mouth, can behave as pathogens elsewhere in the body,” said Dr. Mark Herzberg, a researcher at the University of Minnesota Dental Research Center.

Recently, researchers have linked bacteria that cause gum disease with coronary artery disease, stroke and chronic infections.

In addition, pregnant women with gum disease can pass the bacteria to their fetuses. Researchers estimate that oral disease is responsible for as many as 18 percent of the 250,000 low birth-weight babies born every year in the United States.

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