Dose-response relationship between water fluoride levels and the category of questionable dental fluorosis

There is a dose-response relationship between the prevalence of the questionable category of dental fluorosis as reported by various authors and the drinking water fluoride level. While the possibility that chance could have produced this trend cannot be conclusively ruled out, a distinct pattern of increasing prevalence with increasing water fluoride level can be discerned. Such a pattern is not compatible with the concept of a threshold level for the action of fluoride ion on the enamel organ.