A Cochrane systematic review of the effects of water fluoridation on caries concluded that there is some evidence that it can reduce the incidence of caries of both deciduous and permanent dentition in children.

However, many of the studies are old and are not of high quality; http://www.cochrane.org/CD010856/ORA...nt-tooth-decay.

This paper is relevant in the context of the claimed link between levels of fluoride in water and IQ score; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4265943/.

The authors looked at 1037 children who were born in Dunedin, NZ in early 1973. Some lived in areas where the water was fluoridated, others did not. There was no significant difference in IQ scores between the two groups, assessed either as children or as adults.

Community water fluoridation has been available in many countries since the mid-20th century. Quoting from the article; "No dramatic historical decreases in IQ have been seen following widespread implementation of [community water fluoridation] or worldwide introduction of fluoride toothpastes; instead, historical comparisons have documented substantial IQ gains across countries since the mid-1900s." See the article for details and references.

I think that this provides good evidence that community water fluoridation is not a risk factor for impaired cognitive function.

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