"The preponderance of scientific evidence supports the continuation of this policy," he said. "That would be the result of any fair-minded and balanced review of the material available to us."
It came as the government opposed a private members' bill from Sinn Fein proposing that the fluoridation of water supplies be halted immediately. However, it has pledged to set up a working group to examine issue.
Independent TD Catherine Murphy said that when people were going to have to pay for water, many of them would want to be able to choose not to have it fluoridated.
Fluoridation was introduced in the 1960s to improve the quality of children's teeth and costs around €4m a year.
About 68pc of the population getting water from their local authority are covered. Water in rural areas is generally not fluoridated.
During the Dail debate, Sinn Fein TD Brian Stanley said that 98pc of people in Europe no longer drank fluoridated water.
"We are the only country with a state-wide policy of mandatory fluoridation and local authorities cannot make the decision to stop the process," he said.
However, about 60pc of people in the US drink fluoridated water. And a 2002 survey found there was a higher rate of tooth decay among children under five in the North – where the water is not fluoridated.
Fianna Fail environment spokesman Barry Cowen opposed the Sinn Fein bill to abolish water fluoridation, saying the practice had been endorsed by reputable international bodies such as the World Health Organisation.
"To date there has been a significant reduction in the proportions of decayed, missing and filled teeth of people living in areas supplied by fluoridated drinking water when compared to those in non-fluoridated areas," he said.