WEST PALM BEACH — Within about a year, the county’s 400,000 water consumers will be sipping small doses of what some call a tooth-decay salve and others say is a government-endorsed poison.

After about four hours of listening to county staff and county residents, medical experts and college professors, county commissioners voted 4-2 Tuesday to add fluoride to the county’s water supply. Commission Chairwoman Karen Marcus and Commissioner Mary McCarty voted against the measure, as they did 12 years ago. Commissioner Tony Masilotti was absent.

“I think the overwhelming evidence supports the positive effect of fluoride,” said County Commissioner Jeff Koons, who resurrected the idea of fluoridating the county’s water supply this summer. “We just do not have the dollars to be able to fight the diseases. We do have the dollars to prevent the diseases.”

Commissioners Burt Aaronson, Addie Greene and Warren Newell joined him in supporting fluoridation, a practice that has been used nationally for 50 years.

County commission chambers were filled and folding chairs were set up outside near television monitors to handle the throng who offered their cheers and applause throughout the afternoon. At one point, the crowd waved yellow fliers that read “OOFHA: Optimum Oral Health For All.”

Advocates and anti-fluoridaters used medical experts, the research of Nobel Prize winners, the words of current and former U.S. surgeon general, scientific studies and graphic photos of tooth decay to make their cases. A gaggle of Palm Beach Community College dental services students, all dressed in purple scrubs, came to the podium in pairs to voice their support. Another speaker later criticized the school for what she called brainwashing the students and using her tax money to do it.

“As long as there’s a controversy about whether people want it or not, government shouldn’t force it on them,” McCarty said.

Fluoride occurs naturally in the county’s drinking water. The county’s action will raise the amount from 0.2 parts per million to 0.8 parts per million. County officials estimate the cost of buying equipment to fluoridate the water at from $500,000 to $600,000, with a $75,000 annual cost for maintenance and chemicals.

More than 70 percent of Floridians drink from public water supplies with added fluoride. All of Broward and Miami-Dade counties, but for two small Miami-Dade communities, drink fluoridated water. Stuart and Martin County will add fluoride next year, and most of St. Lucie County drinks fluoridated water. A little more than 25 percent of Palm Beach County residents, close to 300,000 people in Belle Glade, Boynton Beach, Delray Beach, Pahokee, South Bay, Wellington and West Palm Beach, get fluoridated tap water.

Under commissioners’ noses, the South Florida Citizens for Safe Drinking Water set up a display of Wheaties, Fruit Loops, Gerber white grape juice, tomatoes, lettuce and cabbage, with labels indicating how much fluoride they contain, some as much as 45 parts per million, to show that people get plenty of fluoride already. A fluoride proponent denounced the labels as dramatically incorrect.

Critics found fault with the chemicals used to fluoridate water, argued that people have access to fluoride in common foods and that drinking fluoride is much less effective in preventing cavities and tooth decay than brushing with fluoride toothpaste.

“When I learned about fluoridation coming to my community, and I wanted somebody to tell me that arsenic and radium and cadmium and lead were not going to be added to my drinking water, no one could tell me that,” said Lee Marlow, a Wellington resident and parent.

Opponents also point out that most toothpastes carry warning labels about the toxicity of fluoride.

“There are no studies on the actual substance you’re going to put in the water,” said Jeff Green, director of the San Diego-based Citizens for Safe Drinking Water. “We’re not here to talk about reducing tooth decay. If we were, we’d be talking about dental hygiene and nutrition and what part that plays, and we’d be talking about pulling the vending machines from the hallways of schools. Why are you going to mass medicate at a higher level in your community than what a doctor can prescribe?”

Advocates say once fluoride is absorbed into the bloodstream, it becomes part of saliva, which contacts the teeth and protects all day, as opposed to the few hours of protection toothpaste provides. They say plenty of studies show fluoride is safe for people of all ages and does not cause illnesses. They say it is the best way to serve the community’s poorest residents, who might not have access to good dental care. “Water treatment is for disease prevention,” said Dr. Michael Easley, director of the National Center for Fluoridation Policy and Research in Buffalo, N.Y. “If we didn’t need to prevent diseases we wouldn’t have public water systems.”

Commissioners heard residents’ tales of growing up with fluoridated water and having a life free of dental problems. They heard that government agencies are simply afraid to take back an untested stance they’ve held for 50 years. They heard that a lifetime supply of fluoride through water costs $38, compared with $100 for a single filling. They were told that children exposed to fluoride accumulate lead in their blood that makes its way to their brains and causes hyperactivity and learning disabilities and ultimately destroys inhibitions and induces violent crimes.

Commissioner Addie Greene said that as one of nine children who grew up poor but drinking fluoridated water, without cavities, she found Tuesday’s decision an easy one. Commission Chairwoman Karen Marcus said her vote against the measure showed she was simply trying to be cautious.

“To me, less is always better,” Marcus said, but added that the issue now is settled.

Not if opponents have their way. They asked commissioners to pass a law requiring anything added to the water supply to be proven safe and effective, and they said they might sue. And the last time commissioners approved adding fluoride — in 1988 — they reversed themselves three years later.