A new study that shows tooth decay is worsening among young children in Calgary should be of compelling interest to people here in Waterloo Region.

In 2011, Calgary city council decided to stop adding fluoride to its drinking water supply. A year earlier, residents of the City of Waterloo had decided to do the same thing. In a referendum, 50.3 per cent of Waterloo voters said no to fluoridated water.

Fluoride in drinking water, of course, is proven to prevent tooth decay, which is the most frequent illness that children suffer other than the common cold. Its benefits are universally available to rich and poor alike, at low cost to the public.

It is a strategy recommended by many authorities including the World Health Organization, the U.S Surgeon General, and the Canadian Dental Association. Local dentists fought to keep Waterloo’s fluoride, but the people had spoken, and it was removed.

Now, a study published in the journal “Community Dentistry and Oral Epidemiology” shows that Grade 2 students in Calgary, with three years’ exposure to non-fluoridated water, had an average of 3.8 more cavities in 2013-14 than they did in 2004-05.

The study examined 5,000 children in Calgary and Edmonton, which continues to fluoridate its water. Cavities also increased in Edmonton, but at a slower rate.

The study has been questioned. The information about cavities in each city was taken from dental hygienists who went to schools and counted the number of decayed, filled and extracted teeth.

The sample sizes in each city were different; the early (or “control”) sample in Calgary is significantly smaller than the Edmonton one. And also, the results only hold for children’s “baby” teeth. Regarding permanent teeth, Calgary students were slightly better off after fluoridation stopped. Why would that be so?

Still, this study is important. There is a clear conclusion that dental health deteriorated after fluoridation ended.

Here in the Region of Waterloo, public health officials say they are “monitoring” the situation, but offer no other details.

Surely, given the evidence from Calgary, it makes sense for researchers here to do the same kind of study of dental health in the region, comparing the situation before and after fluoridation in Waterloo. Many families in Waterloo may have new questions about fluoridation, and they deserve new answers.

Until the 2010 referendum, Waterloo was the only city in Waterloo Region to fluoridate its drinking water, and it had been that way for 43 years.

But the weight of time and custom was dislodged by anti-fluoride activists who argued that they just didn’t want fluoride in their drinking water. There can be no real conversation between people who argue a position based on public health, and others who argue the opposite based on individual freedoms.

The anti-fluoride camp won, but by the tiniest of margins. The city could pose the question to voters once again. Even if it does not, there is a strong public interest in understanding the consequences of the actions taken in Waterloo.