Effect of femtosecond laser and sllica-coating on zirconia framework-veneering ceramic bonding, surface chemistry and crystallographic changes

The aim of this study was the assessment of various surface conditioning methods upon zirconia framework veneering ceramic bonding, crystallographic changes, and surface chemistry. 91 prepared zirconia specimens were randomly assigned to 4 groups (n = 18) according to conditioning method: Group SB: Air-borne-particle abrasion with 50 mu m Al2O3; Group R: Tribochemical silica coating; Group FL: Femtosecond-laser application; Group Si25: argon/oxygen plasma (8:1 in flux) film deposition on the zirconia surface for 25 min and Group Si49: as in Si25 but only 49 min. The veneering ceramic was fired upon the zirconia surface and the interface of the framework-veneer assemblies were subjected to shear force using a Universal Testing Machine (1 mm/min). Three specimens from every group were analyzed with profilometry and SEM. Data were statistically analyzed using a One-way ANOVA and Tukey's test for multiple comparisons (alpha = 0.05). Failure modes were obtained and SEM-EDX was used to identify tetragonal to monoclinic transformation phase change. Group Si49 (32 +/- 3) presented the highest mean bond strength values (MPa) followed by Group Si25 (28 +/- 6) being not significant from one another (p > 0.05). Groups SB (15 +/- 5) and R (16 +/- 5) did not show significant difference (p > 0.05), being significantly less than that of Group FL (22 +/- 6) (p < 0.05). All groups presented predominantly mixed failures. Silica-based coating was most effective in terms of bond strength, minimal flaws and transformation in the zirconia tested.