Fluoride is to be added to Milton and Kaitangata water supplies if the Clutha District Council gets Government money for the job.
But the jury is still out on whether a third town - Tapanui - will also receive the chemical, which health experts believe reduces tooth decay.
The council had just one month, when confirming its annual plan, to consider the move, but at its full meeting on Thursday it unanimously agreed to fluoridate both Kaitangata and Milton supplies if it got full Ministry of Health funding for the capital works needed.
It has deferred a decision on Tapanui until the town's water plant is upgraded.
It is not yet known when the council will hear if it has secured the money it needs.
The Otago District Health Board and the council polled all three communities on the issue at last year's local body elections.
Nearly two-thirds of voters in Milton and Kaitangata supported the introduction of fluoride, but Tapanui was evenly divided.
Board dental services manager Dr Dorothy Boyd addressed the council this week on the issue and said while it was clear Milton and Kaitangata wanted fluoridation, the result was closer in Tapanui.
However, she still believed there was support for the move in the West Otago township.
In a report prepared for the council, she said international, national and local data all show people who live in fluoridated communities have less tooth decay.
It was a safe, cheap and effective way of preventing tooth decay and was supported by reputable groups including the Ministry of Health and World Health Organisation, she said.
"While opponents of water fluoridation frequently cite concerns about its possible impact on general health, in New Zealand populations with fluoridated water, the only noticeable health change has been significantly better oral health."
The council was also encouraged to fluoridate Kaitangata water in a letter from the Kaitangata and Districts Promotions group which said Balclutha residents had had fluoride in their water for many years with no adverse reactions to their health.
The letter stated that "we feel there is no longer equity for all ratepayers in the Clutha district as some areas are not being given the same dental health options".
The council has already set aside money for fluoridating Milton and Kaitangata water supplies if it gets government funding to upgrade the schemes.
