This study is an attempt to obtain further information concerning the mechanism of action of the fluoride ion in the control of dental caries. Polished surfaces of enamel treated with sodium fluoride solutions for periods varying from five minutes to thirty days and samples prepared by etching with acid before and after exposure to sodium fluoride were studied with the electron microscope. Another phase- involved electron diffraction studies of the crystalline composition of the surfaces of enamel slabs before and after similar treatment.
Few visible surface changes were noted when the treatment with sodium fluoride was given less than seven days. Small amounts of surface deposits were seen after seven days and greater amounts after a fifteen and a thirty day exposure. The deposit was removed by prolonged washing with distilled water. The result of the relative acid solubilities of enamel untreated and treated with sodium fluoride was inconclusive and