During the last four years we have been investigating mineral factors that can ( potentially interact with fluoride because of their ability to form insoluble complexes with fluoride in the gastrointestinal tract or because of their chemical similarity to fluoride, using the albino rat as an animal model. All of the weanling rat studies shared a common aim in that each was concerned with fluoride absorption and utilization bioavailability) as a model for the fate of fluoride originating from foods prepared with fluoridated water. These studies provided new information because the dietary fluoride levels (2 or 10 ppm as NaF) represented nutrition rather than fluorosis unlike previous studies by others. The 10 ppm dietary fluoride level used in all of our studies, for example, produced a bone fluoride concentration similar to that found in children ingesting fluoridated (1 ppm) water. Furthermore, the levels of the other mineral factors were standardized to provide 1/5 normal, normal, and 5 times normal levels in contrast to non-nutritional, gastric intubation studies. During the final phase of the previous award period we also applied what we learned about nutritional effects of other mineral factors on fluoride absorption and retention, and fluoride uptake by developing bone and molar teeth to studies involving the transfer of fluoride from maternal to offspring tissue. Based upon completed studies, we believe that we have uncovered a concept that can explain why some dietary mineral factors significantly influenced fluoride bioavailability (chloride, calcium, magnesium) while others did not (zinc, iron, lead, iodide). Specifically, the mineral factor had to be present in the diet as a molar ratio, with respect to fluoride, in excess of 30, and the number of electrons in the outermost orbital shell of the physiologically charged ion had to be identical to that of fluoride (6 electrons). To further substantiate this hypothesis, we have proposed additional studies involving mineral factors that conform to these criteria. The influence of a mineral factor on maternal transfer of fluoride to offspring is also proposed based upon a significant relationship found in growing rats. In this case, we would have the opportunity to determine if the relationship found influenced caries (dental decay) resistance of offspring molar teeth.
