Experts say there is still not enough information to say whether fluoride should be added to water.
A report compiled by the Medical Research Council spells out several areas where more work is needed.
Adding fluoride to water is backed by health and dental experts including the World Health Organization.
Studies have shown adding fluoride to the water supply is the most cost-effective way of getting it to people, especially children who are at a high risk of tooth decay.
Although fluoride has been shown to reduce dental cavities, it has also been linked with dental fluorosis, a condition relating to the appearance of teeth.
There have also been fears fluoride could be linked to other conditions, including cancer.
Fluoride occurs naturally in earth’s crust, so it gets into rocks, and from there into the water supply in some areas of the world.
But there is still a debate over whether it should be artificially added to water supplies in the UK.
The MRC report says most research was carried out several decades ago.
Since then, they say, many more people use toothpaste with fluoride in it, so more work is needed to take that, and other factors, into account.
The MRC researchers found no evidence fluoride was linked to cancer, or hip fractures, but again called for further research.
The specific areas the MRC recommend should be looked at include: –
* How much fluoride an individual is exposed to
* If there is any difference in the way fluoride is absorbed from naturally and artificially fluoridated drinking water
* The effects of water fluoridation on dental cavities in children and adults, given the widespread use of fluoride toothpaste
* Comparing the extent of dental fluorosis in areas with fluoridated and non-fluoridated water.
Dr Paul Harrison, director of the MRC Institute for Environment and Health, who chaired the group which compiled the report, told BBC News Online much of the research had been done too long ago to be applicable now.
“Because of the widespread use of toothpastes and other dental healthcare products containing fluoride, we need a better understanding of how much fluoride we’re all absorbing,” he said.
“It’s also important to know if there are any differences in the uptake of fluoride from natural and artificial sources.”
He said there was no reason to think water fluoridation was responsible for any adverse health effects, but he said there was a lack of research in some important areas.
Following the MRC’s conclusions, the Department of Health is to commission a project on the absorption of fluoride.
Health Minister Hazel Blears said the Chief Medical Officer and Chief Dental Officer would be asked to advise on the implications of the MRC’s findings on the government’s policy on fluoridation.
She said: “This report demonstrates once again that water fluoridation is an important and effective method of protecting the population from tooth decay and reduces inequalities in dental health.
“There is nothing in this report to suggest any reason why water fluoridation should not be considered as a public health measure in areas where dental health remains a serious problem.”
Water companies hope the report will stimulate government action.
Pamela Taylor, chief executive of UK Water, told the BBC: “Water companies are really stuck in the middle of all this, with people arguing on either side.
“What we want is the government to use this report as a breakthrough. We want them to sit down with us and talk about a sensible way forward.”
The British Dental Association (BDA), which supports the targeted fluoridation of public water supplies, is calling on the department to act quickly.
John Renshaw, chairman of the BDA’s executive board, said: “The report is good news for all who care about children’s dental health, especially children from socially deprived backgrounds who suffer most from tooth decay.
“The report underlines once again that fluoridation reduces tooth decay and gives reassurance on any wider health issues related to fluoridation.
He called for further research to be done urgently and said: “The more time we waste now, the more children will miss out.”