Influence of surface treatment of contaminated zirconia on surface free energy and resin cement bonding

Influences of contamination and cleaning methods on the bonding of resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (IPS e.max ZirCAD) specimens were contaminated with saliva and cleaned with tap water (SC) or by application of 37% phosphoric acid (PA), Ivoclean (IC), or additional airborne particle abrasion (AB). Specimens without contamination served as controls. After application of Monobond Plus to the surface of the specimens, resin cement was mixed and inserted into a mold. Surface free energies of the specimens were determined by measuring contact angles. Surface treatment and storage conditions significantly influenced bond strength, while there was no significant interaction between the two factors. Surface free energies of the SC and IC groups were significantly lower than those of the other groups. Additional AB of saliva-contaminated zirconia increased the strength of bonding with the resin cement as well as increased surface free energy.