Surface Characteristics of Hydroxyapatite and Enamel after Adsorption of Fluoride-Containing Macromolecules

In this study the adsorption of two fluoride-containing polyelectrolytes with different hydrophobic properties on hydroxyapatite is investigated. It was found that the adsorption of the macromolecule was accompanied by the uptake of fluoride, but at a higher rate and with higher amounts than the polymer itself. The influence of the polyelectrolytes on the surface properties of hydroxyapatite and whole enamel was investigated by zeta potential determinations and contact angle measurements, respectively. It was observed that adsorption of very minor amounts of these macromolecules had a remarkable effect on the zeta potential of hydroxyapatite. The original zeta potential of ––9 mV was increased to relatively high positive values. Furthermore, adsorption of the most hydrophobic polymer on the enamel resulted in a poor wettability of the surface by water. Contact angles around 90° were observed, indicating the hydrophobic character of the treated surface