When Calgary, Alberta decided to remove fluoride from its drinking water in 2011, the rate of tooth decay in Calgary children increased found a new study. The research, published in the journal Community Dentistry and Oral Epidemiology, compared rates of tooth decay among second-grade students in Calgary and Edmonton, a city 300 km north of Calgary that still adds fluoride to its drinking water.

The decision by cities around North America to remove fluoride from drinking water has been rather controversial. Medical research, to date, has found no harmful effects of adding fluoride to public water supplies and have long argued the benefits of doing so. Yet, opponents of the practice have continued to argue against medical science and claim that fluoride can actually lower a child’s IQ level; a claim that has long since been debunked.

“We designed the study so we could be as sure as possible that [the increased tooth decay] was due to [fluoride] cessation rather than due to other factors,” said Lindsay McLaren, a researcher at the University of Calgary’s Cumming School of Medicine who led the study. “We systematically considered a number of other factors and in the end, everything pointed to fluoridation cessation being the most important factor.”

McLaren said the cause and effect are clear because of the way they designed the study.

In 2011, Calgary’s city council voted 10-3 to remove fluoride after citing insufficient medical evidence that it was necessary or offered any benefit.

“We as a council have to show some leadership here,” Ward 3 Coun. Jim Stevenson said in 2011, after the decision to remove the fluoride. “I would really question our right to put [fluoride] in, but I don’t question at all our right to remove it.”

Dentists, however, did not agree with the decision and continued to argue for fluoridated water as an ideal and cost effective method for fighting tooth decay, especially for those who cannot afford to visit a dentist regularly.

“It’s not unusual for us to see a child with almost full-mouth decay in the population that we’re looking at, and considering that we’re in Calgary, we shouldn’t be seeing that degree of disease here and we are,” said Denise Kokaram, of the Alex Dental Health Bus. She finds the results troubling because she believes that it could have been fully prevented if not for the ill-informed actions of the city council. “And to think of that rising, and those children suffering and in even more pain, when it’s such an easy thing to remedy to remedy or, at least, assist with,” said added.

Alex Dental saw 1,700 children in Calgary last year, and Kokaram said nearly 50 percent of them suffered from tooth decay.

American cities such as Portland, Oregon have also made the decision not to add fluoride to their water supply after citing health risks, most of which are perpetrated by conspiracy theorists, and not backed by medical research. With new data coming out of Canada, one must wonder if cities in the United States and others around Canada will take note and rethink making rash decisions based on bad information. Multiple studies in the past have shown an increase in dental health was needed in lower income populations in the U.S. and coupled with the findings in Calgary, it should be clear that one solution is fluoridating the water supply.

No study as has been released looking at cities such as Portland and compared it to cities that do add fluoride to the water, but it seems the time for such a study is now. The Calgary study looked at 600 children between 2004 and 2005 before the fluoride was removed from the water supply, and then researchers looked at data from nearly 3,500 children in both cities from 2013 and 2014, after the removal. Researchers saw a significant increase in tooth decay in children whose permanent teeth had begun coming in, a finding they did not believe they would find given the short time between the removal of fluoride and the study. Researchers had set out to gather information on children primary teeth and were surprised by the significant rise in permanent, making their finds more alarming in their opinion. The benefits of doing similar studies in other parts of North America would be greatly beneficial.

The Calgary study will certainly help arm supporters of fluoridation and gives solid medical evidence that the addition of fluoride to drinking water is a positive step for public health, especially in low-income communities when visiting dentists is far rarer as it’s an unaffordable task.