Mechanical properties and bonding potential of partially stabilized zirconia treated with different chemomechanical treatments.

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.