Electron Probe and X-Ray Diffraction Microanalyses of Human Enamel Treated in vitro by Fluoride Solution

Abstract

Fluoride uptake, topographic distribution, and effect on human dental enamel following topical treatment (for 4 min, 8 min and 72 h) with an acidulated fluoride-phosphate solution have been studied by means of electron probe X-ray microanalysis and X-ray diffraction. The samples examined were divided into a non-washed group, and a washed group from which excessive and loosely bound F had been eliminated from the enamel. The topographic distribution of fluorine was demonstrated by electron probe X-ray microanalysis. In the non-washed samples, an outer layer with a higher concentration of F, and adjacent to this another layer having a moderate concentration of F, were observed. After a prolonged washing about 90% of F of the outer layer was eliminated, whereas that of the inner layer persisted. X-ray diffraction analysis shows the presence of CaF₂ in non-washed samples; the lines of CaF₂ disappear after prolonged washing. On the other hand, a displacement of the apatite lines was observed in all treated samples, corresponding to a shortening of the parameter a of the unit cell, due to the replacement of the OH^–– by F^–– in the crystalline network. These results show that by topical treatment of enamel with an acidulated fluoride-phosphate solution, an accumulation of F in the surface layers of the enamel is produced, partly as CaF₂ and partly as fluorapatite.

Effect of Fluoride in Phosphate Buffer Solution on Bonding to Artificially Carious Enamel

“…Fluoride may be incorporated in a soluble (CaF2) and/or permanently bound (fluoroapatite) form. In vitro studies have shown that fluoride applications deposit a reaction product coating of CaF2 on the anatomical surface of enamel 21,22) , and that fluoride is also permanently incorporated into the enamel during application [23][24][25] . It is highly probable that CaF2 creates mineral deposition in the porous zone of enamel and increases the microhardness 26) , thereby resulting in increased bond strength.…”

Effects of CO₂ laser irradiation combined with fluoride application on the demineralization, mechanical properties, structure, and composition of enamel

“…Peaks for β-TCP were also observed in the specimens laser-irradiated with 2.0 and 4.0 W. After laser irradiation with 4 W, all peak intensities decreased, indicating that the surface of the enamel melted partially and the structure changed, becoming amorphous-like, reducing its acid resistance. Because the XRD spectra for hydroxyapatite and fluorapatite are similar, it is difficult to identify the spectra obtained from Groups L and F. Previous studies reported that calcium fluoride formed on the enamel surface after fluoride application [31][32][33][34] . The relative atomic concentration of Group FL (11%) obtained from the XPS analysis was similar to that of fluorapatite, and the F 1s and Ca 2p spectra obtained for Groups L and FL were similar to those obtained for standard fluorapatite materials (Fig.…”

Fluoride Profiles in Dental Plaque in vivo Formed on Fluoride Pre–Treated Human Enamel

“…Such access probably facilitates the delivery of buffering power and topical agents such as fluoride to the plaque-enamel interface. Saliva is not the only potential source of fluoride, however, the enamel surface is known to take up and to contain large amounts of fluoride [Weatherell et al, 1972] some of which is in a relatively unbound form and can diffuse out from the enamel [Baud and Bang, 1970]. This could be a source of fluoride for the plaque.…”

“…Recent data have indicated that much of this may reside in the outer layers of the plaque associated with the salivary interface Kato et al, 1997]. It is possible that fluoride can be released from enamel surfaces after fluoride treatment [Baud and Bang, 1970]. What is unclear, however, is whether fluoride taken up by the underlying enamel could release fluoride into the deeper plaque adjacent to the enamel surface at risk.…”