The Dáil has debated a Private Member's Bill on a proposed ban on the addition of fluoride into the drinking water supply.
Independent TD Catherine Murphy said it was right for people to be sceptical and questioned expert opinion that fluoridation does not cause ill-health.
Her technical group colleague, Finian McGrath, said he has concerns about fluoridation.
He said: "If in doubt, leave it out."
Citing Holland and Germany as countries with good public health policy that do not put fluoride into the water, he said Ireland should be conscious of putting fluoride in the water.
Minister of State Alex White rejected the bill.
He said he accepts that it was put forward in good faith and he is prepared to continue to make public details of studies into fluoridation.
He said the public is entitled to have more information about fluoridation.
Sinn Féin's Brian Stanley said it is unfortunate that the minister was so dismissive of the arguments.
He said that the Department of Health will not reveal the ill-effects of fluoridation.
He added that the Government should distribute it in tablet form and not force people to take fluoride in drinking water.
"98% of Europe cannot be wrong," Mr Stanley said.
A vote on the bill will take place next Tuesday and is expected to be opposed by the Government and Fianna Fáil.