Fluoride proponents declared victory Tuesday night in their battle to keep the cavity-preventing chemical additive in the Las Vegas Valley’s public water supplies.

Supporters gathered in a West Sahara Avenue dentist’s office and toasted early returns indicating that more than 57 percent of voters had decided to keep fluoride in the valley’s drinking water. That margin held with 100 percent of precincts reporting.

Opponents conceded that defeat was almost certain. They blamed a $50,000 pro-fluoride advertising campaign by the Clark County Health District, which they called an inappropriate injection of public funds into a political campaign.

“I just think they were using money that was public money. That was my money coming against me,” said Suzanne Felts, who turned her East Sahara Avenue health-food store into a center of the loosely organized anti-fluoride campaign. “I don’t think that’s fair.”

Clark County Question 1 asked voters if the Southern Nevada Water Authority should cease adding fluoride to the water system serving virtually every home in the valley. The proponents’ group, comprised in large part of dentists and public health workers, called the apparently higher percentage of “no” votes a victory in their fight against an epidemic of pediatric tooth decay in the Las Vegas Valley.

“Oral health in our community won,” said Louise Helton, the chairwoman of Citizens for Healthy Smiles.

Fluoridation also appeared to be gaining the support of majorities of voters in Salt Lake City and San Antonio, where questions of whether to begin fluoridating water were on local ballots.

In recent months, Las Vegas Review-Journal and lasvegas.com polls indicated a much tighter race between the pro- and anti-fluoride groups, with the most recent poll showing a slight edge for fluoride opponents.

Proponents on Tuesday night said that those numbers likely resulted from confusion over the awkwardly worded ballot question — “Should the water authority and each public water system in the county that serves a population of 100,000 or more cease the fluoridation of the water?”

They said they believed that last-minute public campaigning and media attention helped dispel that confusion, which masked overwhelming support for fluoridation.

Dentist James Kinard said Clark County’s influx of more than 500,000 new residents in the 1990s, many of whom came from areas that have had fluoridated water for decades, also helped bolster support for the “no” side of the ballot question.