Influence of surface treatments and resin cement selection on bonding to densely-sintered zirconium-oxide ceramic

Objectives. To evaluate the effect of surface conditioning on the microtensile bond strength of zirconium-oxide ceramic to dual-cured resin cements. Methods. Eighteen cylinder-shaped zirconium-oxide ceramic blocks (Cercon (R) Zirconia, Dentsply) were treated as follows: (1) Sandblasting with 125 mu m aluminum-oxide (Al2O3) particles; (2) tribochemical silica coating using 50 mu m Al2O3 particles modified by silica; (3) no treatment. Each ceramic cylinder was duplicated in composite resin (Tetric Evo Ceram, Ivoclar-Vivadent) using a silicon mold. Composite cylinders were bonded to conditioned ceramics using: (1) Calibra (Densply Caulk); (2) Clearfil Esthetic Cement (Kuraray); (3) Rely x Unicem (3 M ESPE). After 24 h bonded specimens were cut into microtensile sticks that were loaded in tension until failure. Data were analyzed using two-way ANOVA and Student-Newman-Keuls test for multiple comparisons (p < 0.05). Failure mode was recorded and the interfacial morphology of debonded specimens was observed using a scanning electron microscope (SEM). Surface topography and ceramic average surface roughness were analyzed under an atomic force microscope (AFM). Results. Significant changes in zirconia surface roughness occurred after sandblasting (p<0.001). Bond strength of Clearfil cement to zirconia was significantly higher than that of Rely x Unicem and Calibra, regardless of the surface treatment (p < 0.001). When using Calibra, premature failures occurred in non-treated and silica coated zirconia surfaces. Significance. The phosphate monomer-containing luting system (Clearfil Esthetic Cement) is recommended to bond zirconia ceramics and surface treatments are not necessary. (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.