More New Zealanders could have fluoridated drinking water next year.
It comes after a law change pulls power from councils and puts the decision to add fluoride into community drinking water into the hands of Director-General of Health Dr Ashley Bloomfield.
"I'm very, very pleased to see this decision around fluoridation," he said on Wednesday.
Bloomfield said his team would provide advice to him, "and I sign off on fluoridation for communities across the rohe (regions)".
"This will have a major impact, not just on child oral health but on inequities in child oral health."
Associate Health Minister Ayesha Verrall said over half of New Zealand's water supplies are not fluoridated.
"Six thousand children a year go to hospital for operations because of tooth decay. It is a really important health problem to prevent."
She said that Bloomfield would "get data from unfluoridated water supplies across the country and will identify which of those are ready and are most in need of fluoridation", early next year.
"We think it will take us from 50 per cent fluoridation, over time, to 80 per cent."
Water fluoridation was discussed during election 2020's Press Leaders Debate.
Both leaders were asked for their views on the fluoridation of water, while $32 million a year was going towards putting children under general anaesthetic to pull out teeth.
Collins said she grew up without fluoride in her water and said she could tell the difference as her son grew up with fluoride in his, only having one filling.
"I utterly agree with it."
Ardern said she supported fluoridation to keep people healthy. Ardern said she didn't have the numbers to progress legislation, while Collins quipped, "you didn't ask us".
The law change passed on Tuesday with support of all parties.