EDX-analysis of fluoride precipitation on human enamel

One mechanism of action for the anticaries effect of topical fluoridation is through precipitation of CaF₂. In this in vitro study energy-dispersive x-ray spectroscopy (EDX) is used as a semiquantitative method to detect enamel fluoride-precipitation under the influence of acidic and neutral pH-value and absence or presence of a salivary pellicle. Crowns of 30 human caries-free third molars were quartered into four specimens and the enamel surface ground flat and polished. Two specimens each were stored in human saliva (120 minutes pellicle formation). Teeth were randomly allocated into 6 treatment groups: NaF_a (experimental acidic sodium fluoride; 12500 ppmF^-, pH 4.75); NaF_n (experimental neutral sodium fluoride; 12500 ppmF^-, pH 7.0); GB_a (acidic gel base; 0 ppmF^-, pH 4.75); GB_n (neutral gel base; 0 ppmF^-, pH 7.0); AmF-NaF_a (experimental acidic amine/sodium fluoride; 12500 ppmF^-, pH 4.75); EG_a (acidic amine/sodium fluoride; Elmex Geleé, CP-GABA GmbH; 12500 ppmF^-, pH 4.75). Each gel was applied for 60 seconds to one specimen with and one specimen without pellicle. Two specimens served as controls (no gel, without/with pellicle). Atomic percent (At%) of O, F, Na, Mg, P, Ca was measured by EDX. ∆At% and Ca/P-ratios were calculated. EDX could semi-quantify superficial enamel fluoride-precipitation. Only specimens treated with acidic fluoride gels showed fluoride-precipitation, a salivary pellicle tended to decrease At%F.