Volume 69, pages 723-727, 1990
Water fluoridation reduces cavities only by a half-cavity in a typical child aged 5 to 17.
The Brunelle & Carlos research was published in the Journal of Dental Research, The paper was the official analysis of the data gleaned in the largest survey of dental caries ever undertaken in the US. The survey was conducted by the National Institute of Dental Research. It cost $3.6 million and 39,000+ children were examined in 84 communities.
Initial analysis by Dr. Yiamouyiannis looked at the raw data, obtained under the Freedom of Information Act. His analysis found no significant difference in Decayed Missing and Filled Teeth (DMFT) of the permanent teeth of children whether they lived in fluoridated, non-fluoridated or partially fluoridated communities.
Brunelle & Carlos looked at a more sensitive measure of tooth decay, Decayed Missing and Filled SURFACES (DMFS). There are 128 tooth surfaces in a child's mouth. (16 teeth with 5 surfaces and 12 (6 front top and bottom) with 4 surfaces = 80 + 48 = 128.)
For children (aged 5 - 17 years) who lived all their lives in fluoridated (number of children= 8165) or non-fluoridated communities (number of children = 8233) Brunelle and Carlos found an average difference of 0.6 tooth surfaces, i.e. this is less than 1% of the tooth surfaces.