The Food and Drug Administration (FDA) approved the health claim for bottled water containing between 0.6mg and 1mg per litre of fluoride.
A model statement would state that "drinking fluoridated water may reduce the risk of dental cavities/ tooth decay", the FDA said, although the claim cannot be used for waters marketed directly at infants.
The move opens up a new avenue in the fast-growing bottled water market, but will also be seen as controversial at a time when potential health risks linked to fluoride remain unclear.
The FDA said a review of government health reports on fluoride between 1991 and 2001 showed the tooth decay claim was valid.
Around 150m Americans currently have fluoridated tap water, a policy advocated by the Centers for Disease Control in 2001. "Widespread use of fluoride has been a major factor in the decline in the prevalence and severity of dental caries (i.e. tooth decay) in the US and other economically developed countries," it said.
Some health professionals have even raised concerns that growing consumption of bottled water meant people could damage their teeth by missing out on fluoridated tap water. Many bottled waters do not contain fluoride.
The Food Standards Agency in the UK has broadly agreed with the FDA stance on fluoride. It says water containing one part per million fluoride appears to cut the risk of tooth decay.
This may encourage soft drinks and water firms to apply for fluoride health claims in the European Union (EU) too. EU member states have just begun taking the first applications for health claims under new, EU-wide legislation, introduced last week.
The potential risks and growing controversy associated with adding fluoride to water may put some producers off, however.
Authorities in Scotland have so far refused to allow fluoridated tap water due to fears it may be associated with bone, stomach and thyroid problems.
And, a US study published this year found that boys were five times more likely to get a rare form of bone cancer if they drank fluoridated water at levels considered safe by the FDA, compared to boys who drank non-fluoridated water.
The study, completed by Dr Elise Bassin, was published in Cancer Causes and Control, the official journal of the Harvard Center for Cancer Prevention.
"The findings raise fundamental questions about the wisdom of adding fluoride to tap water," said Richard Wiles, senior vice president of the Washington-based Environmental Working Group, an influential consumer watchdog.
Critics say there is little evidence suggesting fluoride is dangerous at the levels it is often found in water. The British Thyroid Association agreed earlier this year there was no proven link between fluoridated water and thyroid disorders.
Health concerns in the UK were also doused in February by Lord Warner, of the UK government's Department of Health.
"Based on the current information available and the dietary intakes estimated from the 1997 Total Diet Study, no adverse effects other than mild to moderate dental fluorosis would be expected to be associated with fluoride intake from food, either in adults or in children, at the intake levels in the UK," he said, quoting a 2003 report from the UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment.
The safe daily fluoride intake for UK adults is 0.05mg per kg, the Department of Health says.