A backwards step for anti-fluoride campaigners, with councillors in Hamilton voting to restore it.

The chemical treatment was stopped last year, but a referendum showed overwhelming public support for fluoride.

Anti-fluoride campaigner Trevor Crosbie is now challenging the referendum - saying it's not a strong enough mandate.

"We don't know what the 60-odd thousand who didn't vote really feel.

"You just don't know so you can't call that a mandate for anything."

Councillor Ewan Wilson says it's a nonsense claim.

"We elect prime ministers and political parties based on who participate in the democratic process.

"If you can't be bothered enough to vote I have very little time for your concerns."

Mr Wilson says while he respects anyone's right to question a decision, a judicial review may not be necessary.

"It's always dangerous when the tail's wagging the dog, and the minority try to override the rights of the majority."

And three giant billboards used as part of Waikato District Health Board's pro-fluoride campaign in Hamilton, will be taken down today.

DHB spokeswoman Mary Anne Gill says it's been a costly campaign.

"We spent $47,000 on our pro-fluoride campaign, $8000 of that on billboards and banners.

"It is unfortunate that the DHB has had to spend so much time and effort on the referendum when there are so many other challenges in health."