Seventy per cent of Hamilton ratepayers voted to return fluoride to the city's water supply after the council took it out in July.
The council sat through a costly tribunal on the subject earlier in the year and promptly voted 7-1 to get rid of fluoride, which had been added to the water for 47 years.
Five of the councillors removed themselves from the tribunal, including the three elected members of Waikato District Health Board - Ewan Wilson, Pippa Mahood and Martin Gallagher - because the DHB's mandate is to support fluoridation.
However, councillor Wilson soon sought a referendum, which Mayor Julie Hardaker voted against.
Ms Hardaker said the council had made a decision and residents did not want a "flip-flopping" council, but she agreed to support the outcome.