X-RAY STUDY OF FLUORAPATITE FORMATION DURING THE FLUORIDE TREATMENT OF POWDERED DENTAL ENAMEL

¹ Department of Chemistry, Indiana University, Bloomington, Ind.

Two x-ray methods are described for the direct determination of whether an apatite sample is dominantly hydroxyapatite or dominantly fluorapatite. In one, conventional powder diffraction technics are used with particular attention to means of collimation and of sample mounting to insure optimum resolution. By measuring the distance from the line at d = 2.81/2.80 Å to the line at d = 3.44 Å, it is possible to distinguish between the two apatites. In the other method, a curved crystal monochromator is used to insure sharp lines, and sodium chloride is used as an internal standard. Again, the two apatites may be distinguished from each other. Samples of dental enamel treated with fluoride reagents reveal a persistence of the hydroxyapatite structure even when treatment is so severe that much calcium fluoride is formed. It is concluded that, under the conditions used, fluorapatite is not the dominant product in the treatment of enamel with fluorides.