MANCHESTER — Voters in Auburn and Derry will learn as early as today whether they can vote Tuesday on the fluoride that the Manchester Water Works puts in the drinking water supply.

Without an order from the court, voters in Manchester, Bedford, Goffstown, Londonderry and Hooksett — but not Derry and Auburn — will be voting on whether to fluoridate or not to fluoridate.

Fluoride is touted by public health officials as a means of reducing tooth decay in children.

A lawyer argued at a hearing in Hillsborough County Superior Court yesterday that voters in Auburn and especially Derry — where 44 percent of the population drinks fluoridated water from Manchester — are being disenfranchised.

With only three business days left before the election, Judge Philip P. Mangones said he would get his order out quickly.

Attorney Jed Callen, representing state Rep. Barbara Hagan and others opposed to fluoride in the public drinking supply, urged the judge to order the state to furnish fluoride ballots to Derry and Auburn.

Callen asserted that Derry and Auburn are being denied equal protection under the law by being denied a vote. He said no one will be harmed if the two towns vote and the votes are disallowed later.

Assistant Attorney General Orville Fitch argued for the Secretary of State that the legal challenge was filed too late and the request for an injunction should be thrown out.

Callen countered that the plaintiffs responded “lightning fast” — within 21 days of finding out the Manchester Water Works had determined Derry and Auburn would not vote on the fluoride issue.

Fitch said state and local election officials would be greatly overburdened if balloting on the fluoride question is ordered at the last minute for Derry and Auburn.

He said if Derry and Auburn don’t want fluoride in their water they can dig wells or find another water wholesaler.

“There is no constitutional right to have public water. There is no constitutional right to have water without fluoride,” Fitch said.

Manchester voters approved fluoridation by a slim 653-vote margin four years ago, but the state Supreme Court declared that vote invalid because the outlying towns did not get to vote.

In the interim, the city water works has been injecting fluoride into the water supply going to Manchester and surrounding communities.

On July 1, new legislation took effect requiring a vote on fluoride by all of the municipalities with 100 or more connections to a water supply.

A simple majority by all of the towns voting on Tuesday will determine whether the water works continues to put fluoride in the water or turns off the spigot.

According to statements made in court yesterday, the Manchester Water Works notified the Secretary of State in June that Auburn and Derry weren’t eligible to vote.

Auburn only has 91 connections to waterlines from Manchester and doesn’t meet the 100-connection cutoff set by the new law to get to vote on the issue, according to the water works.

The water works determined that Derry residents cannot vote because Manchester sells water wholesale to Derry and water customers pay the town of Derry, not the Manchester Water Works.

Callen said 15,000 Derry residents, or 44 percent, are drinking city water but they have no right to vote on fluoridation.

He said all voters in Londonderry, where only 2.7 percent of the residents are on city water, will cast ballots. At the same time, 4.9 percent of the people in Auburn get Manchester water but they won’t be voting.

After the hearing, Callen said if Judge Mangones refuses to issue an injunction, there won’t be time for a Supreme Court appeal before the election. But the outcome of the vote could be challenged later, he said.

“We would probably challenge its validity because it excluded two large groups that plainly had a right to vote based on the statute,” Callen said.

The fluoride issue is being hotly debated in the communities that will vote Sept. 14.

But Derry water superintendent Thomas Carrier said yesterday there didn’t seem to be a lot of interest in the issue now, although a few people had questions four years ago.

Manchester Health Officer Fred Rusczek and water works director Thomas Bowen attended yesterday’s court hearing.

Rusczek was approached by John William Hirzy, a senior scientist at the Environmental Protection Agency’s Office of Pollution Prevention and Toxics. He was there to testify that Manchester is putting hydrofluorisilicic acid — not fluoride — in the water and the acid may contain small amounts arsenic, lead and other contaminants.

That subject did not come up yesterday because Callen withdrew his request for a court order requiring ballots to state that hydrofluorisilicic acid is being put in the water.

Former U.S. Surgeon General C. Everett Koop will address the fluoride question at 11 a.m. today at the Dartmouth-Hitchcock Clinic.

Hirzy asked Rusczek if he could come to the session and debate Koop, but Rusczek said, “We don’t decide public health issues by debating.”

Koop, reached by telephone, said he never debates.

“I don’t ever debate anybody. The science on fluoride addition to public water supplies is sound and those who oppose it do not have equally good science to oppose it,” Koop said.