ATLANTA - Tooth decay in young children's baby teeth is on the rise in the United States, a worrying trend that signals the preschool crowd is eating too much sugar, according to the largest government study of the nation's dental health in more than 25 years.

The study also noted a drop in the proportion of non-elderly adults who have visited a dentist in the past year -- a possible indicator of declining dental insurance.

But there was some good news: Older children have fewer cavities and adults have less periodontal disease than in the past, and more of the elderly are retaining their teeth.

"Overall, we can say that most Americans are noticing an improvement in their oral health,'' said the study's lead author, Dr. Bruce Dye of the National Center for Health Statistics.

Dr. Darryl Smith, the newly installed president of the Canadian Dental Association, said that no comparable statistics exist in Canada, and the most recent cross-country perspective dates back to 1972.

But anecdotally, he suggested the situation in Canada concerning tooth decay in baby teeth mirrors that of the United States.

"I have a very rural based practice myself and for a number of years I have been personally concerned that I'm seeing a lot more dental decay than I have, actually, any time in my career,'' he said from Valleyview, Alta.

"And many of my colleagues, whether or not you're in the city or in a rural environment, are suggesting the same thing.''

As well, he said fewer visits to the dentist by seniors is believed to be a problem in Canada.

But Smith said good data are required to confirm the observations _ and statistics won't be available until 2009 when results come in from a major survey being launched this year by Health Canada.

In the U.S., experts are concerned about the prevalence of cavities in baby teeth of children ages two to five. It increased to 28 per cent in 1999-2004, from 24 per cent in 1988-1994, according to the report.

Tooth decay in young children had been decreasing for 40 years. Some studies have suggested the trend might have ended, but the new report contains the first statistically significant proof the trend has reversed, dental experts said.

One reason is that parents are giving their children more processed snack foods than in the past, and more bottled water or other drinks instead of fluoridated tap water, Dye said.

"They're relying more on fruit snacks, juice boxes, candy and soda'' for the sustenance of preschoolers, he said.

Other experts agree diet is at least part of the explanation for the rising cavity rates.

"The same things contributing to the obesity epidemic can also contribute to tooth decay,'' said Dr. Gary Rozier, a dentist who teaches public health policy at the University of North Carolina.

Inadequate dental care may also play a role. Cavities in young children can form very quickly, and parents should begin bringing their children to the dentist at age one, said Dr. Joel Berg, chairman of the University of Washington's Department of Pediatric Dentistry.

Parents also must help their young children brush properly. "Preschoolers don't have the dexterity to really clean their teeth,'' Berg said.

Baby teeth naturally fall out as children age, but dentists say untreated decay can spread and is too dangerous to go untreated.

Rotten baby teeth are treated with fillings or _ if the decay is extensive _ extraction. But baby teeth fill certain spaces in the mouth, so their early removal may lead to crowding when adult teeth come in.

The study is based on an annual federal survey of about 5,000 people. It includes detailed in-person health interviews, and medical and dental examinations by health care professionals.

The study averaged the findings from surveys done in 1988-1994 and compared them with the average results from surveys done in 1999-2004.

The results are being reported Monday at a meeting of the American Association for Public Health Dentistry in Denver.

Experts were heartened that the study found that cavities in permanent teeth decreased to 21 per cent of children in 1999-2004, from 25 per cent in 1988-1994.

That may be at least partly due to the growing prevalence of dental sealants, a plastic coating applied to teeth that protects against decay. About 38 per cent of children and teens ages 12 to 19 had dental sealants in the most recent set of surveys.

Some of the other findings:

  • Among senior citizens ages 65 and older, the percentage with complete tooth loss dropped to 27 per cent, from 34 per cent.
  • Moderate and severe gum disease in adults ages 20 to 64 dropped to five per cent, from 10 per cent. Gum disease in seniors dropped to 17 per cent from 27 per cent.
  • Tooth decay in the permanent teeth of children ages six to 11 dropped to 21 per cent, from 25 per cent. Tooth decay in youths ages 12 to 19 dropped to 59 per cent, from 68 per cent.
  • The percentage of adults who said they'd been to a dentist in the previous year dropped to 60 per cent, from 66 per cent.