Surface energy of non-corroded and corroded dental ceramic materials before and after contact with salivary proteins.

After sintering and autoglazing, the surface free energy of seven different dental ceramic materials was determined by contact angle measurements using a Dynamic Adsorption Tester and three different standard probe liquids before and after in vitro corrosion and also before and after incubation with human whole saliva. The surface free energy was calculated from the Young-Dupré equation, and the polar and non-polar components were determined. The total surface free energy (range 50 +/- 5 mN/m) did not differ significantly between the different ceramic materials or between corroded and non-corroded specimens. The basicity of the surface persisted after corrosion, although reduced to a lower level, which probably reflects ion exchange processes at the exposed surfaces. After saliva incubation, the basic (gamma-) component of the surface free energy increased, which may be interpreted as the result of salivary proteins binding to the predominantly basic (gamma-) surface with their anionic groups, orienting their cationic sites towards the bulk phase. Selective adsorption of proteins to biosurfaces will no doubt influence both microbiological colonisation and cell adhesion, although the exact mechanisms are not known.