Surface Roughness Effect on the Bonding of Y-Tzp Ceramics

Objectives: One of the most important failure problem of zirconia crowns is the bonding of core and veneer. The purpose of this study was to investigate the effects of roughness after surface treatments on the bonding between zirconium core and veneer ceramic.

Methods: Fifty discs were randomly divided into five groups of ten (Lava, 3M Espe, Seefeld, Germany). For each group different surface treatments were applied: sandblasting (S), wet grinding (G), acid etching (A), plasma (P), and control group (C). After the treatment, profilometer was used to assess the influence of surface treatments on the surface roughness of the specimens. The morphology of surface treatments were evaluated by Atomic Force Microscopy (AFM). Each zirconia discs were veneered with veneer ceramic (Lava Ceram, 3M ESPE, Seefeld, Germany) using a specially designed aluminyum mold. An universal testing machine was used for shear strength test at a crosshead speed of 0.5 mm/min. Statistical analysis was conducted with one-way ANOVA, Tukey's pairwise multiple comparisons, Kruskal-Wallis test and Pearson correlation test.

Results: The mean values of surface roughness (Ra) of the specimens were 0.984, 0.817, 0.769, 6.049, 0.107 for control, sandblasting, plasma, wet grinding, acid etching respectively. S, P, A groups were not significantly different from C. Significant increase in Ra was identified for W compared with the C group. The mean shear strengths were 279.77 N, 265.00 N, 201.77 N, 272.30 N, 208.24 N for control group, sandblasting, plasma, wet grinding, acid etching respectively. S and W groups were not significantly different from C group. P and A reduced core veneer bonding compared with the C. The effect of surface roughness on the bonding between zirconia core and veneer ceramic was not significantly different (p> 0.01).

Conclusion: Different surface treatments on zirconia ceramic surfaces were not significantly influence the bonding of core veneer ceramics.