PORTLAND — Oregon’s dental professionals are unified on one point: Tooth decay — especially among kids — is out of control.

More than half of children ages 6 to 9, or about 66,000 children, have had a cavity, according to a 2012 statewide survey. Children from low-income households saw twice the rate of untreated decay.

The question dividing the dental community, however, is how to solve the problem.

The state Board of Dentistry, which regulates all providers, has come down against one treatment method that many dentists say holds promise in stopping the spread of tooth decay: the use of silver nitrate.

Silver nitrate is U.S. Food and Drug Administration-approved as an antimicrobial agent and is commonly used in things like wart removal and water purification. But many dentists have been using it on an off-label basis instead of the traditional drilling and filling in of cavities.

Those in favor of the treatment say it’s an inexpensive way to stop tooth decay, especially for low-income populations, while those opposed point out that there hasn’t been any U.S.-based academic research that supports its use. It also requires several visits to apply and is known to leave a black crust where it’s applied.

The board voted at its meeting Friday against a measure that would have allowed dental hygienists and assistants to, under the supervision of a dentist, apply silver nitrate onto patients’ teeth.

“I feel like we’re talking about allowing people to do stuff that really has no scientific basis,” said Board Member Julie Ann Smith, a Portland oral surgeon. “I have a problem with that.”

Dentists already are allowed to use silver nitrate on patients, but the change would have expanded the scope of the practice by allowing them to direct their staff to apply the treatment, said Patrick Braatz, the board’s executive director.

More than a dozen people, most of them dental professionals, spoke passionately on the subject at a public hearing Thursday night. Opinions were split almost evenly, with seven speaking in favor of the change and six speaking against.

Steven Duffin, a Keizer dentist, said he’s witnessed the “miracle” silver nitrate represents in stopping tooth decay. Duffin, who uses a combination of silver nitrate and fluoride varnish on cavities, said the use of silver nitrate in dentistry dates back more than 100 years.

“This is not something new,” he told the group Thursday. “This is not a communist plot.”

Perhaps the weightiest voice on Thursday was that of Steven Timm, a Bend dentist and president-elect of the Oregon Dental Association. Timm, speaking on behalf of the ODA, emphasized that the FDA has approved silver nitrate for external use only and the substance is highly toxic to the gastrointestinal tract. If ingested, it can lead to coma, paralysis and death, he said.

Timm also pointed to the lack of clinical trials validating the substance’s use in preventing cavities, and questioned the impact on patients of the black crust that’s known to follow its application.

“Let’s not experiment on our patients in Oregon,” he said.

The Board of Dentistry isn’t the only group to oppose the use of silver compounds. In January, a subcommittee of the Oregon Health Evidence Review Commission, the group that decides which conditions are and are not covered under the state’s Medicaid program, known as the Oregon Health Plan, decided there wasn’t enough evidence to support the use of silver compounds to treat cavities. The decision means that silver compounds — a broad term that includes silver nitrate and silver diamine fluoride, a similar agent that’s not FDA-approved — are not covered under OHP for such procedures.

Despite the controversy surrounding silver nitrate, it’s being widely used to stop tooth decay in patients, both young and old, in Central Oregon.

Redmond-based Advantage Dental Services, which provides care to nearly 200,000 Medicaid recipients in Oregon, uses silver nitrate on patients of all ages, said Mike Shirtcliff, Advantage’s president and CEO. Advantage, the largest Dental Care Organization in Oregon, operates four clinics in Central Oregon, including one in Bend.

Shirtcliff testified in favor of silver nitrate’s use at Thursday’s meeting, arguing that it allows dentists to control infections and keeps people out of the hospital.

Similarly, Frank Mendoza, a dentist at the Warm Springs Health and Wellness Center Dental Clinic, located on the Warm Springs Indian Reservation, began touting a “new dental program” to patients in the Sept. 4 issue of the reservation’s newspaper, Spilyay Tymoo.

Mendoza, who declined a request for comment, wrote in an editorial that one drop of silver nitrate is enough to treat all the cavities in a patient’s mouth. It’s applied with a tiny dental brush and followed by fluoride varnish to strengthen the tooth enamel, a process that requires about five monthly visits, he wrote.

“When tooth cavities are treated this way, within a short time the cavity itself turns a dark color and sometimes black: This is good!,” he wrote. “This means the silver nitrate is working to stop the infection and keep the cavity from going deeper into the tooth.”

But Brandon Schwindt, vice president of the Board of Dentistry and a pediatric dentist in Tigard, said at the board meeting on Friday that silver nitrate doesn’t kill the bacteria that causes the cavities, nor does it eliminate the cavities.

The use of silver nitrate turns a blind eye to the real problem, which is that dentistry as a profession is failing to treat children, he said. While Schwindt said he feels for patients who don’t have access to dental care, an unproven treatment is not the solution.

“People who don’t have access to appropriate care, do they deserve an unsafe car?” Schwindt said. “An unsafe hospital bed? A building that’s not up to code?”

Fellow board member Patricia Parker, a Hillsboro dentist, countered that silver nitrate might be a great solution for elderly patients. She said she would have loved to have had silver nitrate available to her mother, who didn’t receive any dental care while living in an Alzheimer’s unit.

“There is a huge gap in the nursing home system for elderly people,” she said.

Many dentists in Bend don’t accept OHP recipients because they don’t profit from providing the care, Shirtcliff said in an interview after Thursday’s meeting. He said he thinks the unspoken reason many dentists oppose the use of silver nitrate is economic.

“If we actually stopped decay and there weren’t any more fillings to fix, guess what?” he said. “There wouldn’t be any more crowns to do. There wouldn’t be any more money to make. This is more about economics than it is about dentistry.”