The Calgary study you mention is fatally flawed. The study omits data showing that the spike in decay mostly occurred when fluoride was still in the water.

The study is riddled with problems and is "not a valid assessment of the effect of fluoridation cessation," says Dr. Trevor Sheldon, Dean of Hull York Medical School who is also a scientist who specializes in studying the effectiveness of health care interventions, including fluoridation.

The study determined Calgary's pre cessation cavity rate based solely on a small survey conducted 6 years prior to fluoridation ceasing, even though a much more comprehensive survey was conducted just 1 year prior to fluoridation ending.

The omitted survey conducted in 2009/10 shows that most of Calgary's increase in tooth decay occurred while Calgary was still adding fluoride to its water.