The Government says adding fluoride to more drinking water will help cut rates of tooth decay in children.
Moves are underway for DHBs to take over the decision-making role on water fluoridation and Health Minister Jonathan Coleman's announced $12 million in funding for infrastructure costs.
But anti-fluoride groups are concerned it will lead to compulsory fluoridation.
Around 2.3 million New Zealanders currently have access to fluoridated water. Dr Coleman says increasing access will improve oral health.
"This change would benefit over 1.4 million New Zealanders who live in areas where networked community water supplies are not currently fluoridated," he says.
"We know that children have up to 40 per cent less tooth decay in fluoridated areas compared to areas without fluoride."
But Fluoride Free NZ disagrees and says the Minister's cherry-picking statistics.
Spokesman Don Church says the Minister should refer to his own Ministry of Health statistics.
"They show a very small benefit for five year olds and if you look at the statistics in 12 year olds there's very little difference. It's all hype."
"It is mass medication against people's will, against freedom of choice," says Mr Church.
Councils currently decide whether fluoride is added to the drinking water, but that's likely to soon change.
The Health (Fluoridation of Drinking Water) Amendment Bill, which is awaiting its second reading, transfers the decision-making power from local councils to DHBs.
"Decisions would be based on the assessment of health-related evidence and local needs. Recognition that fluoridating water is the single-most important initiative to improve dental health, particularly child dental health, is long overdue and I'm sure this move will be welcomed by the wider community."
If that passes, DHBs are expected to start making decisions about water fluoridation in 2018.