TUESDAY, May 22 (HealthScoutNews) -- A cup of black tea may be just what the dentist ordered. Compounds found in black tea leaves fight cavities and can reduce that nasty plaque, a new study says.

Made from the fermented leaves of the same plant that produces green and oolong teas, black tea is enjoyed by 80 percent of the world's tea drinkers, says study leader Christine D. Wu, a microbiologist and professor of periodontics at the University of Illinois College of Dentistry

The study is being presented today at the 101st general meeting of the American Society for Microbiology in Orlando, Fla.

"Although green tea has been shown to lead to reduction of dental cavities in humans, very little research had been done to see if the more popular black tea would also promote oral health," says Wu.

Cavities are caused by bacteria produced when simple sugars are converted into acid. The acid eats away at the tooth, eventually leaving a hole, which may continue to grow and lead to tooth loss.

In a series of three experiments, Wu's team found that compounds in black tea, which act as antioxidants, could kill or suppress the growth of the cavity-causing bacteria, curtailing their production of acid.

Black tea also affected the bacterial enzyme glucosyltransferase, which converts sugar into the sticky matrix material that plaque uses to stick to teeth.

And black tea prevented certain bacteria from clumping with others, reducing the mass and stickiness of dental plaque.

In one week-long experiment, 10 people rinsed their mouths for one minute, five or 10 times a day, with either black tea or water. Those who rinsed with the tea 10 times a day had less plaque on their teeth, less harmful acid in their plaque and less cavity-causing bacteria in that plaque, say the researchers.

Whether the frequency of rinsing played a part was the subject of the second experiment. Rinsing for 30 seconds with black tea, five times at three-minute intervals, prevented growth of plaque-producing bacteria, though one 30-second rinse had no effect, Wu says.

In the third test, conducted in a laboratory, researchers produced cavity-like lesions on extracted teeth and treated them with five, 10-minute rinses of black tea.

The lab test didn't produce results as good as the human tests, because the researchers say the benefits of tea result from a complex interaction between chemical and microbiological forces.

Wu says the study also tested for fluoride, a naturally occurring substance in fermented black tea leaves, but "after seven days didn't see an accumulation of fluoride."

Wu says although the study was small and didn't last long, "these results provide a foundation on which additional experiments and treatments can be constructed."

Wu says, "We have to remember that in order to keep plaque away, one has to brush. Any toothpaste or adjunct is a supplement. Rinsing alone is not going to do it."

But don't substitute black tea for mouthwash quite yet, says Riva Touger-Decker, a nutritionist at the University of Medicine and Dentistry of New Jersey.

Although the study "is a very exciting breakthrough . , opening up a whole new arena for fighting cavities and preventing disease and dealing with plaque, there are so many behavioral factors that come into play" that require more study, says Touger-Decker.

Dr. Donna Mager, a specialist in oral medicine and a dentist-scientist in the department of oral biology at The Forsyth Institute in Boston, says, "Technically, it's difficult to measure plaque. What teeth do you measure? How many? Do you measure the accumulation all over the mouth?"

Mager says such studies are both time consuming and expensive. But, she says the researchers should be commended.

What To Do
Black tea contains caffeine, so think twice before giving it to your kids, says Touger-Decker. Instead, have them "cut back on juices, sugared drinks and have them drink seltzer or water."