Influence of surface treatments on the surface properties of different zirconia cores and adhesion of zirconia-veneering ceramic systems

Objective The aim of this study was to assess the influence of surface treatments on the surface characteristics of different zirconia cores and the adhesion of the zirconia-veneering ceramic systems by means of strain energy release rate (G-value, J/m(2)). Methods Three types of zirconia cores (NANOZR (NZ), Vita In-Ceram YZ (VZ), and IPS e.max ZirCAD (IZ)) were used. The specimens were divided into four groups in each test according to the surface treatment used; Gr 1 (control; no treatment), Gr 2 (sandblasted), Gr 3 (CH2Cl2 for 60min), and Gr 4 (experimental hot etching solution for 60min). AFM, SEM, EDS, and XRD were carried out. Two types of veneering ceramics (Vita VM9 (V9) and IPS e.max Ceram (IC)) were used for testing the adhesion. The G-value (J/m(2)) was measured with a four-point bending configuration. Following fracture testing specimens were examined with SEM. Data were analyzed using ANOVA and Tukey's test. Results NZ treated with the experimental hot etching solution showed the highest Ra values (206.06±9.98nm) compared with the other groups (P<0.05). The greatest amount of monoclinic phase is measured after sandblasting (19.59%) for NZ, followed by VZ (9.3%) and IZ (6.6%). The NZ/V9 (etching for 60min) group showed the highest G-value (36.02±2.80J/m(2)) among the groups. Mode of failure was mostly cohesive failure within all the bonded veneering ceramic systems. Significance The experimental hot etching solution could be considered as alternative treatment modality to sandblasting for zirconia cores to avoid phase transition at the surface from tetragonal to monoclinic that may be detrimental for the longevity of the zirconia-veneering ceramic restoration.