It’s deja vu for most city residents as they prepare for the third time in 21 years to vote on whether or not they support fluoridation of the Methuen water supply.

The question, which will be posed to voters as part of a special city election in conjunction with the statewide election Tuesday, was put on the ballot at the request of Mayor Sharon M. Pollard after forcing the city’s Board of Health to rescind a vote it took earlier this year approving fluoridation. Pollard publicly denounced the approach the board took with the vote, blasting it for failing to properly notify her, the City Council, the Department of Public Works, and water-treatment personnel that it was planning to vote for such a controversial matter.

”With no consideration of budget issues, they just unilaterally voted for it,” said Toody Healy, Pollard’s chief of staff. ”Her stance is that the process was flawed.”

After the board refused to rescind its vote, Pollard dismissed one of its members and forced public health director Robert Katz to quit. Afterward, the board, with two new members appointed by Pollard, rescinded its vote.

”She wanted to get it on a referendum,” Healy said.

But residents will be voting on a nonbinding referendum, which, no matter what the outcome, still allows the Board of Health to implement fluoridation of the water.

”It’s just a reflection of what people think,” Healy said. ”What it means is that it gives you a good temperature of the public to see where they are. If it’s not a close vote, the board might consider things in a different light.”

Just five years ago, when the question was posed a second time to voters, it was narrowly defeated by 394 votes, with 4,159 residents voting against fluoridation, 3,765 voting for it, and 500 who left their ballots blanks. That was a notable difference from 1981, when a similar question lost by a 1,084-vote margin; that time 5,416 voters rejected fluoridation over 4,332 who were for it, and 695 who left their ballots blanks.

Despite a decrease in voter participation during the two previous elections that featured the fluoridation question, Healy said the population in Methuen as a whole has grown tremendously since 1981, bringing with it a change in demographics.

”Like any other community with growth, things have changed. [There’s been] a lot more development out in the west [side] with newer homes and people with children who may want [fluoridation],” Healy said. ”If it passes, it would be a reflection of changes in the demographics in the community. This is just speculation that people with children would be more prone to wanting that in their water.”

William J. Buckley, interim director of the Board of Health, couldn’t be reached for comment.

According to the US Department of Health and Human Services, numerous well-documented studies have found that fluoride helps prevent tooth decay and cavities. While fluoride is found in many dental products, fluoridation of water is the most cost-effective method, especially in poorer communities, studies say.

Fluoride has also been used experimentally to treat osteoporosis, but results have not been conclusive. For years, fluoridation has been lauded by organizations such as the American Dental Society and the Centers for Disease Control and Prevention as an effective way to prevent tooth decay.

Opponents argue fluoride is a toxin and that, unlike chlorine in water, fluoride does not evaporate.

William Patenaude, chairman of the Methuen Citizens for Safe Drinking Water … Without Fluoride, is doing his best to make sure parents and the rest of the city’s residents vote ”no” come Tuesday.

Patenaude, who ran against Pollard for mayor in 2001, said he was once in favor of fluoridation until he spotted a warning on fluoridated toothpaste that if more than the recommended amount was swallowed, poison control should be contacted.

”Finally I was convinced that this stuff should not even be put in water,” Patenaude said. ”What we’re saying to people is freedom of choice. If there’s any doubt, leave it out, and there’s plenty of doubt.”

Patenaude said he has spent more than $13,000 fighting fluoridation since 1996 and has put up a $2,000 award to be given to someone’s favorite charity ”if you can prove that fluoride is not toxic.”

”Nobody’s given me a call because it’s impossible. So why would you want to put a toxin in the water?” Patenaude said.

Lisa McCrillis, secretary for Methuen Citizens for Safe Drinking Water … Without Fluoride, said the organization has mailed out about 10,000 brochures against fluoride to the community and she is optimistic people don’t want fluoride in the water.

”They have already voted against it twice. They voted what their opinion will be on the subject. I feel that we will win,” McCrillis said.

If residents reject fluoridation, but it is later implemented by the Board of Health, opponents may get a binding question placed on the ballot of the next city or state election by collecting and filing with the city clerk signatures from at least 10 percent of the town’s registered voters within 90 days of the board’s legal notice of its decision.