SIOUX FALLS, S.D. (AP) – Researchers examining the oral health of people living on the Pine Ridge Indian Reservation in southwestern South Dakota found that many members are missing teeth and suffering from periodontal disease, according to a study released Wednesday.

The Colorado-based Center for Native Oral Health Research examined a sample of 292 adults and children for the report. Half of the adults screened had 27 or fewer teeth, many had diseased gums and too few had proper fillings to help combat cavities, the study found.

“We expected the periodontal disease rates to be high,” said Judith Albino, the study's principal investigator and director of the research center. “But I guess we were still surprised. We weren't thinking about how high `high' would be.”

The study also found that 68 percent of screened adults had evidence of some periodontal disease, with 16 percent advanced cases, and 24 percent of adults and 11 percent of children had urgent oral health needs. Children with permanent teeth on average had two decayed teeth, while adults on average had five.

Adults on average had 25 teeth. Adults typically have between 28 and 32 teeth, depending on whether they have their wisdom teeth.

Terry Batliner, the study's director, said there are 10 dentists on the entire reservation, which is roughly the size of Connecticut, serving a population of about 30,000 people. That's nowhere near enough, he said.

“We met a number of children who had never seen a dentist before,” Batliner said. “There's a lot of untreated decay.”

Officials with the American Dental Association, which responded to the study findings late Wednesday, said the findings were disturbing but not surprising. The association heads the Native American Oral Health Project with state dental societies in Arizona, New Mexico, North Dakota and South Dakota to encourage people to “take better command of their own oral health,” according to a statement from association president William Calnon.

“As is the case with most underserved populations, the barriers preventing too many American Indians from achieving good oral health are numerous and complex,” Calnon said. “There is no one-size-fits-all solution.”

Study organizers said the findings were tied to low incomes, as nearly half of Pine Ridge people live below the poverty line. They also blamed what Native Americans eat as their indigenous diet of buffalo, berries and roots has been replaced with more sweetened beverages and fatty foods. And they said there's a shortage of oral health providers on or close to the reservation, making it more difficult to reach dentists.

Training non-dentists, such as licensed hygienists, to practice as dental therapists might help improve oral health, according to the study. It's an approach similar to one that has worked well in Alaska, Batliner said.

But Calnon criticized this approach.

“American Indian communities will never drill, fill and extract their way out of what amounts to an epidemic of dental disease,” he said in his statement, adding that “only oral health and education and prevention will defeat that epidemic.”

Batliner said he agrees that more preventative care is needed on Pine Ridge, but he said that won't treat the cavities and decay that already exist.

The study was funded by the W.K. Kellogg Foundation. The center, which falls under the umbrella of the Centers for American Indian and Alaska Native Health, has begun a separate study that aims to work with new mothers to teach preventative dental care habits, Albino said.