In this in vitro study, examination of the enamel surface morphology after topical application
of an amine fluoride solution with different fluoride (F) content was carried
out. Sound human enamel slabs were treated with an amine fluoride solution containing
either 1.0, 0.5 or 0.25% F for 3 min. during 3 days. All slabs were examined using
scanning electron microscopy and energy-dispersive spectroscopy (SEM/EDS) qualitative
analysis. The globular precipitates were revealed in all treated specimens, regardless
of F content. The distribution of the deposits was more homogeneous in groups
treated with higher concentrations; however, the globules were larger and more cubical
in groups treated with lower fluoride concentrations. These larger globules could be less
soluble and thus serve as a fluoride reservoir for a more extended period and so they
could contribute to the caries preventive effect in professional topical products with lower
fluoride concentration. Following the 24-hour treatment with KOH the precipitates
could be removed; however, the enamel surfaces covered with the precipitates were less
degraded than the untreated enamel. The EDS qualitative analysis showed that the intensities
of fluoride signals were increased with the higher concentration of fluoride in
an amine fluoride solution, while the intensities of calcium signals were decreased. The
enamel surface precipitates were alkali-soluble, but we were not able to demonstrate
that they are pure calcium fluoride
