It shouldn't be up to cities to decide to add fluoride to drinking water, but provincial officials, a Canadian mayor says.

Windsor, Ont., is bucking a national trend and looking at lifting its ban on adding fluoride to drinking water after seeing an increase in cavities among children.

Community water fluoridation is recommended by public health, medical and dental groups, including the Canadian and American Dental Associations, Canada's Chief Dental Officer and the World Health Organization. The U.S. Centers for Disease Control and Prevention called its contribution to the decline in cavities one of the 10 great public health achievements of the 20th century.

Fluoride is a mineral that binds to the enamel of teeth, strengthening them to prevent bacterial decay.

But ever since Canadian communities first introduced fluoridation in 1945, some cities have gritted their teeth at the contentious addition, and the debate continues. Some Windsor city council members initially argued that fluoride could be obtained cheaply from toothpaste and other critics have presented general fears over adding chemicals to water supplies.

A 2018 review by the Canadian Agency for Drugs and Technologies in Health evaluated dozens of studies on the health effects associated with fluoridation. "The evidence in this review supports the protective role of community water fluoridation in reducing dental caries [cavities] in children and adults," the authors concluded.

Decisions left to people with 'no science background'

Last month, the city council in Windsor, Ont., voted to put fluoride back into its water supply after voting to remove it in 2013.

While Windsor's mayor Drew Dilkens is opposed to fluoridation, he doesn't think it should be up to municipalities to decide.

"If there is truly a health benefit of fluoride in the water system that is legitimate and real, it should be decided and mandated for all water systems across the province of Ontario and across Canada. That is not the case. They leave the decision up to people like me with no science background," said Dilkens.

"You have got to make the decision you think is right for your community and I think that mass medicating the entire water supply for the benefit of very few is not the right thing to do. But council voted otherwise. I respect that decision. We will add fluoride back to the water if another municipality agrees with council's decision."

Studies show fluoridation is effective for the broad population, said Dr. Alexandria Meriano, a pediatric dentist in Windsor.

Like Windsor residents, almost two-thirds of Canadians no longer have fluoride added to their municipal water. In British Columbia, Yukon, Quebec, New Brunswick and Newfoundland and Labrador for instance, less than three per cent of the population has fluoride added to their municipal water. In comparison, it's 74 per cent in the U.S. and the CDC aims to increase that to 80 per cent by 2020.

Yemmi Calito's children are patients of Dr. Meriano. The two oldest kids were raised on fluoridated water in Windsor and both have healthy teeth. Her two youngest weren't, and they've had to be treated for serious tooth decay. Calito said their oral hygiene habits are the same.

"The younger two I feel they have more cavities," Calito said. "My little one, my three-year-old, actually had to go have general anesthesia … [about] four weeks ago to get his teeth fixed. They were in pretty bad shape."

Meriano said she's noticed a difference in her patients after the city banned fluoridation. "What I am seeing is more cavities at a younger age and more severe cavities at a younger age."

Dr. Alexandria Meriano supports re-introducing fluoride in Windsor's tap water. (Turgut Yeter/CBC)

The advantage of community water fluoridation is it reaches everyone, not just those seeking dental care, Meriano said.

Like Windsor, Calgary is also seeing a spike in kids' cavities after removing fluoride. One city councillor in Calgary is convinced of its health benefits and thinks the city should vote on putting it back.

The opposition to fluoride is driven in part by "a fear of 'chemicals,' which unfortunately have been synonymous with toxin or poison," said chemistry Prof. Joe Schwarcz. "I think a lot of it comes back to just a lack of scientific knowledge, scientific literacy and fear mongering."

In affluent areas where there's access to dental care, and people receive advice from dentists on how to counsel their kids to use fluoride toothpaste without swallowing it, then there might be an argument against fluoridation, he said.

Almost two-thirds of Canadians no longer have fluoride added to their municipal water. (Craig Chivers/CBC)

"But in communities which are poorer, where there is no access to dental care and where children are not regularly examined in terms of their dental health, the overwhelming evidence is that you can reduce cavities by putting fluoride into the water," said Schwarcz, who heads the McGill Office for Science and Society.

Schwarcz said the debate over fluoridation will never end.

"There will always be people who are convinced that some sort of intervention is going to do them harm. We've seen this over the years not only with fluoride. We've seen them with pasteurization, we've seen it with microwave ovens, with cellphones. Any new technology is initially opposed and then eventually of course when its merit is proven the opposition slowly abates," he said.

"But it never completely goes away."