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plaque that occurs naturally on the tooth surface. The second topical effect comes from fluoridated <br /> water that is swallowed. Some of it then enters the saliva via the bloodstream, which means the fluoride <br /> has another opportunity to become concentrated in dental plaque on the tooth surface. <br /> By the end of the 20th century, when the topical and pre-eruptive effects of fluoride in drinking <br /> water were better understood, most researchers concluded that the main preventive effect of <br /> fluoridated drinking water was topical. One piece of evidence came from studies of people who started <br /> consuming fluoridated water as adults. By then, all of their permanent teeth had erupted, meaning that <br /> the preventive benefit of fluoridated water was due solely to post-eruptive effects. The fact that those <br /> adults developed decay at a lower rate than adults who lived in non-fluoridated areas indicated that <br /> fluoride in drinking water could prevent decay solely on account of its topical effects on erupted teeth. <br /> However, those same studies found that decay rates were even lower in adults who had <br /> consumed fluoridated water in childhood AND in adulthood. This greater benefit from LIFETIME <br /> consumption of fluoridated water occurs because of the additional pre-eruptive effects of fluoride <br /> during childhood. It's difficult to be precise as to just how much additional benefit occurs because of the <br /> pre-eruptive effect in childhood. The best evidence in humans comes from a study of over 17,000 <br /> children aged 6-15 years who provided a lifetime history of their water consumption. Decay rates were <br /> measured in the first permanent molars, which erupt around six years of age. The study showed that <br /> fluoride in drinking water had an overall preventive benefit, reducing decay in by 28% overall, with <br /> about half of the effect being pre-eruptive and one half post-eruptive. In other words, the topical effect <br /> was equivalent to the pre-eruptive effect in this age group. <br /> See Attachment 22 for a detailed response and references. <br /> 32 <br />