ATLANTA – As more Americans are drinking from the bottle instead of the tap, dentists are sending patients home with prescriptions for fluoride.

Most bottled waters contain little or none of the fluoride that’s standard in tap water and is considered essential to hardening teeth and preventing cavities in children. So dentists are urging patients to mix their bottled-water use with tap water or to buy fluoridated bottled water. And dentists are prescribing more fluoride treatments, pills and drops.

“So often, our parents think they are doing the right thing by giving their children bottled water,” said dentist Dr. Kaneta Lott of southwest Atlanta. “But we’re seeing a lot of tooth decay in those same children.” Because widespread drinking of bottled water is a relatively new trend, there are few hard data on exactly how many children’s teeth are being affected by it. But the problem is significant enough that the American Dental Association, at its recent annual session, called for labeling of fluoride concentrations on bottled water.

The federal Centers for Disease Control and Prevention made a similar recommendation in 2001.

Beverage titan Coca-Cola said it has no immediate plans to add fluoride to its bottled water, Dasani, or to go along with labeling requests. But some water bottlers have begun responding to the concern. Dannon Fluoride To Go, marketed at children, hit store shelves in 2000, and you can also buy Crystal Springs With Fluoride.

Concerns about the fluoride gap have risen with the sales of bottled water, which have skyrocketed to $7 billion a year. Almost half of all Americans drink bottled water daily, according to the International Bottled Water Association, getting about a third of their average 5.3 daily cups of water from bottled products.

But parents shouldn’t necessarily worry that they’re putting their children’s teeth at risk.

“There could be fluoridated water at the school, at day care, at Grandma’s house. Fluoride also occurs in some foods,” said Dr. Steve Adair, chairman of the Medical College of Georgia’s department of pediatric dentistry. “If a child eats black-eyed peas canned in Florida in a community that has fluoridated water, he’s probably getting some fluoride that way.”