Three out of five third-graders in Colorado during the 2022-2023 school year had tooth decay, according to the most recent data from the state health department.

Colorado’s finding of a history of tooth decay in 61% of third graders is both in line with the national average and still far too high, said Dr. Karen Foster, a Denver dentist and previous president of the Colorado Dental Association.

Residue from most types of food will weaken teeth over time, but good oral hygiene, community water fluoridation and regular dental care can prevent that damage, she said. “Teeth that are kept clean, kept from sugar exposure and fluoridated don’t experience decay,” she said.

Water fluoridation has become controversial in recent years because of studies that found negative effects from drinking high levels of fluoride, though dentists and public health experts say that levels used to prevent tooth decay in the U.S. aren’t high enough to harm children.

The Colorado Department of Public Health and Environment reported that some water systems in the state add fluoride, while others have enough of the mineral in their water naturally that they don’t need to. It didn’t post a breakdown of systems’ fluoridation decisions. According to the Centers for Disease Control and Prevention, 409 of Colorado’s 947 water systems have fluoridated water, though some, such as Colorado Springs, don’t need to add the mineral because the water picks up naturally occurring fluoride from the surrounding environment.

Water in the reservoirs that supply Denver typically has enough natural fluoride to prevent tooth decay, though Denver Water sometimes adds to its treated water if the supply comes in with a lower-than-expected concentration, according to the utility. Delayed dental visits during the pandemic may have increased the number of kids experiencing cavities, but even in ordinary times, about half of students in that age group had either current tooth decay, or a filling showing they’d had it before.

The rates of kids with tooth decay ranged from a low of 47% during the 2016-2017 school year to 57% in 2003-2004.

The data comes from Colorado’s Basic Screening Survey, which uses a sample of data collected from free dental check-ups offered to public school students in kindergarten and third grade. Kindergarten students were less likely to have had tooth decay than their older peers, but 46% still had a history of cavities or a current one.

About one-quarter of students in both grades had untreated cavities at the time of their screening. Latino and Black students, and those attending schools with more low-income families, were more likely to have both a history of cavities and current untreated tooth decay.