Influence of fluoride applications on some physicochemical surface properties of synthetic hydroxyapatite and human dental enamel and its consequences for protein adsorption.

Synthetic hydroxyapatite and human dental enamel (polished and non-polished) were subjected to various fluoride applications, i.e., using solutions of sodium fluoride (NaF), acidulated phosphate fluoride (APF), and stannous fluoride (SnF2). Treatment with APF has a strong influence on the morphology of the apatite. All fluorides, in particular SnF2, make the enamel surfaces more hydrophobic. NaF and APF applications slightly alter the electrokinetic potentials of the surfaces, but SnF2 renders them much more negatively charged. The adsorption of the proteins lysozyme and alpha-lactalbumin on these surfaces can be explained in terms of electrostatic and hydrophobic interactions between the proteins and the sorbent surfaces.