Once upon a time – a bit more than a year and a half ago – some scientists published a study in which they looked at the rates of tooth decay in two large Canadian cities: Edmonton, where the water had been consistently fluoridated since 1967, and Calgary, which stopped its fluoridation program in 2011.

Both cities showed more primary (baby) tooth decay, but the increase was greater in non-fluoridated Calgary, said the scientists.

Their study received a lot of media coverage and a whole lot of hoopla over what seemed like a confirmation of fluoride’s effectiveness. Yet, as a recent column in the Calgary Herald noted,

What was not widely published is that according to the very same study, the number of cavities in permanent teeth actually decreased in Calgary since fluoridation ended. You read that correctly. “For all tooth surfaces among permanent teeth, there was a statistically significant decrease in Calgary . . . which was not observed in Edmonton.” Interesting, isn’t it, that this juicy morsel from the report was never quoted? [emphasis added]

And that wasn’t the only funny thing about the study. Now, a new paper in Community Dentistry and Oral Epidemiology shows that it also had some significant “shortcomings in study design and interpretation of results, and did not include important pertinent data.” Include that data, and you get something far different from what the original team found.

When this third data set is considered, the rate of increase of decay in Calgary is found to be the same before and after cessation of fluoridation, thus contradicting the main conclusion of the paper that cessation was associated with an adverse effect on oral health.

Other problems included a failure to account for variables among risk factors for caries between the two cities and a low participation rate that may have resulted in selection bias, further distorting the results.

“Owing to these weaknesses,” assert the authors of the new evaluation,

the study has limited ability to assess whether fluoridation cessation caused an increase in decay. The study’s findings, when considered with the additional information from the third Calgary survey, more strongly support the conclusion that cessation of fluoridation had no effect on decay rate.

More, fluoridation is just bad policy. For 10 reasons why (plus a link to 50 more), visit IAOMT.org.

Originally posted 2017-10-19 07:09:30.