Two separate studies on tooth erosion indicate that it's on the rise in the U.S. and that acidic drinks are a prime cause of it. They also suggest that you should wait at least 30 minutes to brush your teeth after consuming an acidic beverage.

The chief culprits are acidic drinks, with an assist from sugar.

Tooth erosion is the wearing away of tooth enamel (the tooth's outer covering) by chemicals. It is estimated to affect one in 15 Americans. Many dentists have suspected for some time that tooth erosion is on the rise. A 2008 study indicates that they may be right. The study looked at 900 middle school students in Indiana, Texas and California, aged 10-14. It found dental erosion in about 30% of these students.

Dental erosion initially gives the enamel a smooth and shiny appearance. Because it causes no pain or sensitivity in its early stages, most sufferers aren't even aware of it. But there's only so much enamel coating a tooth. Lose enough, and teeth become more brittle, more sensitive to pain and may even be lost altogether.

The chief culprits are acidic drinks, with an assist from sugar. These include soft drinks, sports drinks, fruit juice and tea. Soft drinks usually contain phosphoric or citric acid. Sports drinks and many fruit juices contain citric acid. A 2009 study using cow teeth showed the erosive effect of citric acid on teeth. Teeth were immersed in either a sports drink or water for 75-90 minutes and then removed. This was an attempt to simulate the effects of sipping on sports drinks over the course of a day. Enlarged photographs revealed the presence of many tiny pits or holes in the surface of the sports drink treated teeth — clear signs of erosion.

Sugar also plays a part because the bacteria present in tooth plaque quickly convert sugar into acid. Saliva eventually helps lower the acidity in the mouth back to a normal level and helps restore minerals to the enamel that were leached away by food acids.

It is generally recommended that people wait around 30 minutes to brush their teeth after drinking acidic drinks. This allows the softened enamel to re-harden before subjecting the teeth to the abrasive scrubbing that occurs during brushing. If you don't, you'll be scrubbing away at weakened enamel and permanently removing some from the teeth — hitting them while they're down, so to speak.

But increased tooth erosion may be due to more than just an increase in soda and sports drink consumption. The manner in which drinking is being done and a lack of fluoride may also play a part.

Drinking soda, juice or sports drinks slowly over the course of a few hours is more damaging to your enamel than simply drinking one fairly rapidly. Similarly, savoring the drinks, holding them in their mouth for a while before swallowing, is a practice best left to wine tasters. It, too, prolongs the enamel's exposure to the softening acidity.

The switch by many to bottled water means that they're drinking little or no fluoridated tap water. The fluoride in the tap water previously strengthened their enamel. And most home water filtration systems also remove the fluoride.

General recommendations for people who are worried about tooth erosion include consuming less acidic beverages and use of a fluoridated toothpaste and mouth rinse. For more specific recommendations, ask your specific dentist.

The study on tooth erosion in middle school students appeared in the March, 2008 issue of Dental Tribune. The study on the effect of sports drinks on cow teeth was presented at the annual meeting of the International Association for Dental Research on April 6, 2009.