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In 2011, Calgary officials removed fluoride from the city’s water. About five years later, new research is warning that removing the mineral that strengthens teeth left kids with more cavities than before.

University of Calgary scientists say that since 2011, Calgary kids saw 3.8 more cavities, extractions and fillings, while kids in Edmonton, where water still has fluoride, saw a smaller increase in tooth decay. In total, Calgary kids had 6.4 issues with decaying in their baby teeth years after fluoride was removed from their water.

“Fluoride is known to have benefits for preventing tooth decay – it inhibits demineralization of tooth enamel, enhances remineralization of tooth enamel, and having it in saliva neutralizes plaque bacteria in the mouth. By drinking water with fluoride, we can prevent tooth decay,” lead investigator, Dr. Lindsay McLaren, of the university’s School of Medicine, told Global News.

McLaren said Calgary’s decision to remove fluoride was “a real opportunity to have up to date and locally relevant information.”

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For her research, McLaren compared the oral health of 5,000 grade 2 kids in Calgary and Edmonton during two timeframes – before fluoride was removed in 2004/05 and after in 2013/14. Her team chose seven and eight year olds because they’ have a mix of both baby and adult teeth.

READ MORE: Alberta children suffering because dental care is out of reach

And parents need to pay attention to baby teeth, according to co-author and dentist, Dr. Steven Patterson, of the University of Alberta.

Kids have 20 baby teeth, on average, with four or five surfaces (the four sides and the top) per tooth.

If baby teeth are exposed to cavities, extraction or infections, they can tamper with the development of new teeth as they grow in the jaw bone. Strength and formation of the permanent teeth could be altered, too.

WATCH: Researchers have discovered Calgary’s decision to remove fluoride from drinking water, they city’s children are getting more cavities. Heather Yourex-West reports.

1:55 Study finds increase in cavities for children since Calgary remove fluoride Study finds increase in cavities for children since Calgary remove fluoride

“They’re not teeth we’re supposed to ignore because we’ll get a new set. Oral health starts at the beginning when teeth come in for young children,” Patterson warned.

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McLaren and Patterson relied on data from a scale that measures decaying, extractions and fillings in teeth. In 2004/05, second graders in Calgary had 2.6 tooth surfaces with issues but by 2013/14, they had about 6.4 teeth with decaying surfaces. That’s an increase of 3.8.

READ MORE: Tooth decay ‘epidemic’ in Canada could be linked to too much fruit juice, study suggests

In Edmonton, where fluoride stayed in the water, tooth decay climbed from 4.5 surfaces to 6.6 – a difference of 2.1.

The duo says this disparity is a “statistically significant difference.”

“That means it’s unlikely for it to be random or chance findings. It’s a meaningful effect and our study was a short-term evaluation so even after only 2.5 to three years, we saw an indication of effect,” McLaren said.

Up to 20 per cent of all baby teeth were affected, McLaren said.

“We’re talking roughly close to a quarter of their primary teeth. What this tells us is there’s a number of kids who have this disease that could be prevented and should be lessened,” he told Global News.

The researchers even controlled for other factors. They figured out how often the kids were brushing their teeth, how much tap water they were drinking and even collected fingernail clippings as samples to test for fluoride.

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“It still pointed out that it seemed to be fluoridation being stopped that had a negative effect on tooth decay in Calgary,” Patterson warned.

READ MORE: Is milk good for your bones? Study casts doubt

The largest effects were found in baby teeth but the researchers note that a lack of fluoride eroded at permanent teeth, too. It’s just that there are differences in enamel so it’s too soon to tell how adult teeth will fare in kids’ mouths as they get older.

WATCH: A new study is putting into question the City of Calgary’s decision to remove fluoride from the city’s water supply. Doug Vaessen has details on how it will impact Calgarians.

1:42 How removing fluoride from Calgary’s water affected kids’ teeth How removing fluoride from Calgary’s water affected kids’ teeth

The data is also up-to-date and locally relevant. Research on removing fluoride in the water in Canada is dated back to 1975, she said. Yet several major municipalities in Canada have already phased out fluoride – Waterloo, Ont. in 2010, Quebec City in 2008, Windsor, Ont. in 2013 and Moncton, N.B. in 2012, along with a handful of regions nearby to Calgary in Alberta.

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Fluoride is still in toothpaste and food and beverages manufactured in regions where the mineral is still in the water, though. The researchers are urging parents to encourage their kids to brush their teeth, and get regular dental care.

The team’s next steps are to collect another wave of data from both cities to see if the trend continues, McLaren said.

They’re hoping their findings will help city officials decide on the controversial issue of keeping fluoride in the water. It was first introduced to public drinking water in 1945.

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Their full findings were published Wednesday morning in the journal, Community Dentistry and Oral Epidemiology. Read the study here.

carmen.chai@globalnews.ca

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