In an old science experiment, a teacher would put a tooth in a bottle of cola to display the perils of sugar; the tooth would disappear in a few days.
Researchers have now demonstrated that non-colas, canned iced teas and even diet drinks also can weaken and erode tooth enamel.
As a result, the average American, who washes down two 12-ounce cans of soft drink every day, is unwittingly making his or her teeth more vulnerable to cavities.
Sugar - a typical 12-ounce can of soda contains approximately 10 teaspoons - isn't the only culprit.
The malic, tartaric, citric and phosphoric acids that impart a nice, tart flavor are particularly corrosive to the tooth's protective enamel coating.
"The sugar does cause problems, but it's nowhere near as injurious as the acids," said lead author J. Anthony von Fraunhofer, a professor of restorative dentistry at the University of Maryland Baltimore.
These acids, he said, draw calcium out of tooth enamel.
He and a colleague exposed dental enamel from healthy extracted teeth to a variety of popular drinks for 14 days. In a surprise finding, some artificially sweetened drinks were more damaging than their sucrose- or fructose-sweetened counterparts. Non-colas were worse than colas.
"It was astonishing to me how bad the non-colas were," von Fraunhofer said. Sodas and flavored teas were tougher on enamel than plain brewed tea, coffee and root beer.
Having soft drinks with a meal is probably less damaging than sipping them without food, which prolongs the exposure to acids, he said. The study was published in the July/August issue of General Dentistry, the journal of the Academy of General Dentistry.