Add this to the collateral damage of the nation's childhood obesity epidemic: young children are getting more cavities in their baby teeth now than they were a decade ago, even as the nation's overall dental health has improved.

That's according to a report released yesterday by the Centers for Disease Control and Prevention, which analyzed data from two six-year periods, 1988 to 1994 and 1999 to 2005. Researchers found that the number of children ages 2 to 5 getting cavities in their baby teeth increased from 24 percent of the population to 28 percent.

The 4 percent uptick is alarming for two reasons, said the report's author.

"This represents thousands and thousands of kids who have at least one cavity in their baby teeth compared to 10 years ago," said Dr. Bruce Dye of the CDC's National Center for Health Statistics.

"It's also significant because for the past 40 years we have documented a continual decline in tooth decay in children as well as adults. This is the first time the trend is going in the opposite direction."

In part, experts blame the increase on the same dietary changes causing a record number of overweight youngsters: constant snacking on processed foods, fewer fruits and vegetables, more sugary drinks at younger ages, including juice in baby bottles and sippy cups.

"I can't tell you the number of kids that come into our waiting room sipping on a Mountain Dew," said Dr. Deborah Studen-Pavlovich, chair of pediatric dentistry at the University of Pittsburgh School of Dental Medicine.

"If you look at the acidic nature of pop as well as the sugar, the bacteria that causes dental caries multiplies in that environment.

"Dental caries are contagious," she added. "If you let them go, they spread to other teeth. I have a 26-month-old coming in this week with 12 teeth to be restored."

On the other hand, she said, "I have patients graduating high school who've never had a filling. They eat candy, but they don't eat it at night and then go to bed without brushing their teeth."

Continuous eating is a factor, she said, because the mouth never gets a chance to restore a neutral pH balance. That, too, gives the bacteria fertile ground.

Children are also drinking more bottled water instead of fluoridated tap water that fights tooth decay.

"We've actually had an expansion of community fluoridated water in the past decade or two, but bottled water is convenient and parents figure it's better than a juice box in their lunch," said Dr. Dye. "But it's not as good as fluoridated water."

He also cited a reduction of tooth-brushing at home.

"Kids still need parental supervision with toothbrushing, but as our lives become more compressed and hectic, skipping brushing saves a minute or two of a busy day."

Healthy baby teeth are important, he said, because they hold the place for adult teeth to come in correctly. In addition, decayed baby teeth expose adult teeth to the same bacteria when they break through the gums, setting off a chain reaction of infection.

Dr. Studen-Pavlovich noted one source of tooth decay that many people may not be aware of: Parents or caregivers with tooth decay can pass the bacteria to young children via shared utensils and cups.

"Moms are the primary caregivers; their nutrition and dental health are important for their children to avoid transmitting the bacteria," she said.

In contrast to the bad news on the pre-schooler front, much of the report showed notable improvements in the nation's dental health. For example:

Decay in the permanent teeth of youths age 6 to 11 decreased from 25 to 21 percent, and among teens it decreased from 68 to 59 percent.

The use of dental sealants (a plastic coating applied to teeth that protects against decay) increased from 22 to 30 percent among the 6- to 11-year-olds, and from 18 to 38 percent among teens.

Moderate and severe gum disease was down from 10 to 5 percent among adults age 20 to 64, and from 27 to 17 percent among seniors age 65 and older.

The percentage of seniors with complete tooth loss dropped from 34 to 27 percent.

Other areas that need to be improved, according to the report:

The number of adults who reported visiting a dentist in the past year declined, from 64 to 60 percent.

Disparities persist along racial, ethnic and economic lines. Some 31 percent of Mexican-American children ages 6 to 11 had decay in their permanent teeth, compared to 19 percent of non-Hispanic white children.

Three times as many children from families below the poverty line had untreated tooth decay as those with higher incomes -- 12 percent vs. 4 percent.

"This report challenges us to increase our efforts to reach those most in need with effective preventive measures," said Dr. William R. Maas, director of the CDC's Division of Oral Health.

The findings were presented yesterday in Denver at a meeting of the American Association for Public Health Dentistry. The full report is available online at www.cdc.gov/nchs.