A new study suggests that tooth decay rates go up when Canadian communities stop fluoridating their water.

The study, published Wednesday in the journal Community Dentistry and Oral Epidemiology, compared Grade 2 students in Calgary, which stopped fluoridating its water supply in 2011 and Edmonton, which still adds fluoride.

It found decay rates for baby teeth went up in both cities between 2004-05 and 2013-14, but the increase was bigger in Calgary (3.8 per cent in Calgary versus 2.1 per cent in Edmonton).

Steven Patterson, who's with the school of dentistry at the University of Alberta and was one of the authors of the study, says he hopes it will get Canadians talking about the issue.

In Saskatchewan, fluoridation has been a controversial topic over the years. Opponents say fluoride is toxic and even at low levels there's a health risk.

Regina does not fluoridate its drinking water, but fluoride is added to the water in Saskatoon, Moose Jaw and other communities.

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Regina's mayor, Michael Fougere, said there are many studies on the topic.

"Is there a direct correlation between fluoride and cavities? Some reports would say otherwise," Fougere said Thursday. "So there's lots of data."

Dr. Gerry Uswak, dean of the College of Dentistry at the University of Saskatchewan, noted people in Regina have more cavities, compared to Saskatoon.

"We do see a difference between the cavity rates in Regina versus Saskatoon, and the decay rate is higher in Regina," Uswak said. "We just have not done the level of assessment that's been done in Alberta."

Uswak said that fluoride in the water seems to be a key factor.

"Based on scientific knowledge we assume that it is probably due to no fluoride in Regina water, but before we could make a pronouncement on that we would have to do a different form of analysis," he said, adding that is something the university would be prepared to do.

In a 1985 referendum, citizens of Regina voted against adding fluoride to the water supply.