Abstract
The reactions of 113SnF2, Sn18F2, Na18F, and APF (acid phosphate fluoride, labelled with 18F) solutions on human dental enamel surface under conditions similar to topical application in vivo were investigated.
The experiments supported the following conclusions.
1) A remarkable accumulation of Sn in or on the enamel surface was found after the runs of repetition with SnF2 solution, whereas a minimum amount of F accumulated as compared with NaF or APF solution.
2) The enamel surface treated with SnF2 solution aquired more remarkable resistance to acid than treated with NaF or APF solutions.
3) After the treatment wtih SnF2 solution, the greater part of Sn taken on the enamel rapidly turned into acid-insoluble compounds.
The major amount of these Sn compounds was found on the enamel surface.
4) Fluoride taken by the enamel from fluoride solution diffused immediately into the surface layer of the enamel. The easy release of these fluorides by decalcification indicated that a fair amount of fluoride in the enamel remains in unreacted form.
5) Statistic analyses, however, revealed no significant correlation between Sn or F uptake and increased resistance of enamel to acid.
6) In the analyses of the Sn/F ratio accumulated on the enamel and the amount of F and the Ca/P ratio released by acid, it could not be shown that the Sn compounds on the enamel are either SnPO4, Sn4 (PO4) 2 (OH) 2H2O, or Sn3F3PO4, as had been formerly reported.
7) Although the enamel surface was polished with Al2O3, a striking variation of Sn uptake by the enamel was found. This variation of Sn uptake might be dependent on both random difference from place to place in one tooth enamel and on individual tooth differences, both of which consist of unknown factors.
F uptake also varied markedly from tooth to tooth, but variation from place to place in one tooth enamel was negligible.
8) Incipient carious enamel took up Sn more strongly than the intact enamel.
