Dentist Larry Levin has made his pitch about the importance of adding fluoride to drinking water several times in recent years to city councils voting on the controversial issue.

He has won some and lost some.

Levin, a past president and current vice-president of the Canadian Dental Association, believes more communities are deciding against fluoridation.

It's frustrating, argues the Hamilton dentist, because he has science on his side.

"You scratch your head wondering why," Levin says. "These big organizations who have studied it have told us that it's safe. Our own physicians have told us that it's safe."

Levin thinks most people who are against fluoridation simply want the freedom to choose what goes in their water.

Fluoride is found in soil, water, some food and several minerals and is added to products such as toothpaste.

Research has shown adding fluoride to drinking water reduces tooth decay. The World Health Organization, Health Canada, various dental associations and provincial medical officials support the effort, especially for children from low-income families who may not have access to dental care.

Opponents argue not enough is known about what they say are possible health risks such as cancer, bone disease and fluorosis, in which too much fluoride causing teeth to discolour.

While federal and provincial governments set guidelines for fluoridation, the decision is left up to municipalities.

Brantford, Ont., became the first Canadian community to add fluoride in 1945 and many others followed. Health Canada reported in 2009, the last time it counted, that about 45 per cent of the population was drinking fluoridated water.

That's dropped to about 37 per cent, Levin estimates.

Canadians Opposed to Fluoridation believes the figure is less than 30 per cent.

"Belief in water fluoridation has become so ingrained in us that it's reflex to just think that water fluoridation is good," says an emailed statement from the group's president, Robert Fleming.

He says fluoride supporters rely on flawed studies and people shouldn't be "medicated" against their will.

"Municipal councillors and other Canadian citizens have been catching on to the fact that artificial water fluoridation is without substantiation. It won't be long now before Canadians are fluoridation free," says Fleming.

Big cities including Toronto, Hamilton, Ottawa, Halifax and Winnipeg fluoridate. Montreal and Vancouver don't fluoridate. Neither do Waterloo and Windsor in southern Ontario.

After several plebiscites, Calgary removed fluoride from its water in 2011. But it could be back on the ballot again.

Mayor Naheed Nenshi said last month that he supports fluoridation and urged people to petition for a plebiscite in the 2017 municipal election.

The call came after the release of a University of Calgary study that compared children's teeth in Calgary with those in Edmonton, which does fluoridate. While there was an increase in cavities in both groups, the increase was higher in Calgary.

Coun. Dianne Colley-Urquhart, a former nurse, says the study has prompted her to rethink fluoridation, which she's opposed in the past.

She says she's especially worried about children's dental health now that plunging oil prices have caused layoffs in the province.

"Families -- they have parents that aren't working. There are no benefits. They're trying to put food on the table, let alone trying to squeeze together a few pennies to go to the dentist."

Colley-Urquhart believes public institutions should provide all municipalities with an expert review of fluoridation, since politicians don't have the expertise to deal with public health issues.

John Sprovieri agrees that municipal councillors aren't health experts and perhaps shouldn't be making the final decision on fluoride.

The councillor for both Brampton and the surrounding Peel region believes fluoride is a "toxic chemical." He stopped drinking the area's fluoridated water four years ago, put a water filtration system in his home and started taking bottled water to work.

Peel council is to vote this fall on whether to remove fluoride from its water.

If the federal and provincial governments support fluoridation so much, Sprovieri adds, they should be making the decision.

"If it's really legitimate that water fluoridation prevents cavities ... then why aren't you taking responsibility and mandating it to the whole population?"

Federal Health Minister Jane Philpott says that she supports fluoridation, but is not considering a change in the government's role.

Levin says it doesn't make sense that so many communities have to debate the issue so many times.

He sides more with Colley-Urquhart, and believes an expert panel should be visiting municipalities grappling with the question so they get all the information they need.

"At the moment, it's whoever turns up at that council meeting to speak to it," Levin says. "There isn't a lot of uniformity to those processes."