WATERLOO — Canada’s top dentist warns that tooth decay may rise in Waterloo if residents vote Monday to end water fluoridation.

“You’re going to look at problems,” Dr. Peter Cooney told an audience of about 50 people, including many fluoridation critics. He warns that children may suffer the most.

“That would be a real pity,” he said in an interview.

Cooney is Health Canada’s chief dental officer. He was the star attraction Thursday at a fluoridation information session held by local dentists at the RIM Park complex.

Cooney and Dr. Dick Ito, a public health dentist, led the audience through national and international research supporting water fluoridation.

They say adding fluoride to tap water, as Waterloo has done since 1967, reduces cavities by 20 to 40 per cent, improving oral health with no known health risks at recommended levels.

“It’s very, very safe,” Cooney said. “It’s cost-effective and it works.”

He fended off concerns raised by critics around the science and impact of fluoridation. “I’ve heard nothing new tonight,” critic Robert Fleming said, after repeatedly challenging Cooney and Ito in a question period.

Fleming disputes the assertion that tooth decay rises when fluoridation ends.

Most Ontario water is fluoridated. The practice is endorsed by more than 90 medical, dental and public health organizations.

But in this region only Waterloo fluoridates its water, which also flows to Elmira, St. Jacobs and part of Kitchener. Residents have twice endorsed fluoridation by referendum and are to vote again Oct. 25.

Critics claim the chemical used to fluoridate water is a threat. They allege various health risks and argue the practice violates personal choice.

Dentists point to studies showing Waterloo has a lower rate of tooth decay than Kitchener and Cambridge.