Purpose: To evaluate the effect of different chemomechanical surface treatments of zirconia on fracture toughness, flexural strength, bond strength of zirconia to composite cement, surface topography, and phase transformation.
Materials and methods: Pre-sintered yttrium-stabilized zirconium oxide blocks (in Coris ZI) were used. Specimens were prepared using a milling machine (Cerec InLab). Specimens for each testing procedure were classified into 6 groups according to the surface treatment applied: group 1: air-borne particle abrasion (ABA); group 2: silica coating; group 3: hot etching solution; group 4: hot etching solution followed by ABA; group V: hot etching solution followed by silica coating; group 6: control. Fracture toughness, biaxial flexural strength, and shear bond strength were tested using a universal testing machine. Surface topography was evaluated using a surface roughness tester and scanning electron microscope. Phase transformation was examined using x-ray diffraction analysis. Data were subjected to one-way ANOVA followed by Tukey's HSD multiple comparisons test at p < 0.05. The strength reliability was analyzed using the Weibull distribution.
Results: Silica coating revealed the highest mean fracture toughness (9.18 ± 0.11 MPa • m½), biaxial flexural strength (1614.1 ± 124.6 MPa), and bond strength value (31.5 ± 5.06 MPa) among all tested groups. Surface topography evaluation revealed variations among the different surface-treated groups.
Conclusions: Silica coating induced significant improvement in the tested properties compared to other treatments. The use of combined treatment of hot etching solution followed by either air-borne particle abrasion or silica coating of the zirconia surface did not provide an added advantage over silica coating alone.