Moves to make it easier for fluoride to be added to drinking water in England and Wales have got the backing of MPs.
Opponents warned this amounted to “mass medication” but a vote for a total ban on fluoridation was lost by 284 to 181.
Water companies have been allowed to add fluoride to supplies since 1985 but few have for fear of legal action.
The new legislation will allow health agencies to force firms to fluoridate water after consulting local people, in order to tackle tooth decay.
The British Dental Association was among those calling for the change, as were former health secretaries Alan Milburn, Frank Dobson, Ken Clarke and Lord Fowler.
But in the free vote, Foreign Secretary Jack Straw, International Development Secretary Hilary Benn and new Conservative leader Michael Howard were among those pushing for fluoridation to be blocked.
Opponents claim fluoride can cause a range of problems, from tooth mottling to cancer, and have threatened to mount a legal challenge on human rights grounds.
One of the leading opponents of fluoridation, Plaid Cymru’s Simon Thomas said: “I hope the declaration will be to say we don’t have the evidence, we don’t have the public support and we don’t have the confidence at this stage, in this bill, to pass such an important public health measure.”
The evidence which did exist in favour of adding fluoride was “weak, contradictory and unreliable”, he argued.
Labour MP James Wray suggested there was enough fluoride in a tube of toothpaste to kill a child.
But junior health minister Melanie Johnson pointed to one study suggesting 15% more children would have no tooth decay if water was not fluoridated.
The measure could prevent the “unnecessary risk” of tooth extractions under general anaesthetic for thousands of children, she said.
“The case is clearly for allowing local communities to decide,” added Ms Johnson.