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Making Sense of the Science
3.5 minutes: Systematic Reviews

Systematic reviews are when a panel of highly qualified scientists are convened to evaluate the most relevant published scientific research on a particular topic following specific guidelines set forth by the panel and the institution that commissions the review.

Such reviews can take considerable time to organize and even more time to conduct. For example, in 2006 the US National Academies of Sciences' National Research Council (NRC) published the results of their 3.5 year review of just about every published study that existed at the time on the effects of fluoride in drinking water.


The National Academies of Sciences is one of the world's most prestigious scientific institutions; often referred to as a Supreme Court of Science.

In addition to the 2006 NRC review, there are 2 other independent systematic reviews that have been conducted on the effects of fluoridated water. The first was published in the year 2000 by the UK's University of York's National Health Services (NHS) Centre for Reviews and Dissemination which at the time was considered the most rigorous and thorough review on fluoridation. The second was published in 2015 and was carried out by the Cochrane Collaboration, an institution often described as providing the Gold Standard in medical scientific evaluations.

The main differences between these three reviews is that the York and Cochrane reviews established very strict inclusion criteria which resulted in many studies not being included because they ranked as too biased and / or lacked sufficient controls and rigours. This means that of the three, the NRC review, looked at even more research which explains why it took 3.5 years to complete.

Also, in addition to it's high standards for inclusion criteria, the Cochrane Institute only reviewed research dealing with the following questions:
- Is fluoridater water cost effective?
- Does it affect social economic status (i.e. does it help the financially disadvantaged)?
- Does fluoridated water reduce tooth decay? 
- To what degree does fluoridated water cause dental fluorosis?

The icon links allow you to see for yourself what the most rigorous scientific and least biased reviews concluded about the effects of fluoridated water.
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