Effect of a surface-active cation on fluoride/enamel interactions in vitro.

After in vitro treatments of bovine enamel with NaF/Zonyl FSC and NH4F in-depth profiles of the chemical composition of the outermost zone of surface enamel were obtained with electron spectroscopy. The most important finding of the study was that after the treatments with nearly neutral as well as slightly acidic solutions of NH4F the ammonium cation was found on the enamel surfaces. Similarly a Zonyl FSC layer was detected on the enamel surfaces after the NaF/Zonyl FSC treatment, while sodium ion was never detected on the enamel surfaces. The implication is that the sorption of these cations plays a role in fluoride-enamel interactions.