But Nationals Victorian leader Peter Ryan said the public had not been consulted and residents deserved input on the water they drink.
The Victorian government plans to add fluoride to water supplies in the Geelong and Ballarat areas by the end of next year at a cost of $1 million.
A Department of Human Services (DHS) report found the project would save more than $220 million over 25 years in improved dental health.
Ryan said the decision was "government by stealth" and the public had been locked out of the debate.
"While I personally support fluoride, I also believe people should have the right to have a say on the issue," he told reporters.
"I think it's a case of the government doing things which have significant implications for people in the community and doing it without consultation."
DHS spokesman Bram Alexander said that while affected residents had not been polled to gauge support, there had been widespread consultation.
"You make decisions for the greater good. This is a public health decision and we don't make public health decisions on dodgy evidence," Alexander said.
"The jury's in on fluoride - it's safe and effective."
Alexander said affected households were mail dropped about the fluoride plan last December.
In February, four public information sessions were held in Geelong and two in Ballarat, and a hotline had been set up to field inquiries, he said.
"Based on a whole range of reasons the decision's been made to fluoridate Geelong and Ballarat because it's an equitable way of providing fluoride to all."
