Effect of Various Veneering Techniques on Bond Strength and Colour Stability of Zirconia / Veneering Ceramic after Hydrothermal Aging

BACKGROUND The purpose of this in-vitro study was to compare the colour stability and bond strength of zirconia-based ceramic restorations after hydrothermal aging using conventional layering, heat-pressing, and multilayer veneering techniques. METHODS One hundred twenty specimens’ core (15 x 10 x 0.7) was fabricated from A2-shade zirconia CAD-CAM blocks (IPS e.max ZirCAD). Specimens were divided into 4 groups for veneering (N = 30): [(layering group (L), IPS e.max ceram), (heat – pressing group (P), IPS press), and multilayer group, IPS e max Cad for 2 different types of cement (cemented with RelyX U200 (M1) and PANAVIA SA (M2))]. Aging was performed for (5 - 55°C, 5000). Colour coordinates before and after aging were measured to calculate colour differences (ΔE00). The shear bond strength test was performed with a universal test unit. The data were analysed using the analysis of variance (ANOVA) and Tukey’s Honest Significant Difference test (alpha = 0.05). RESULTS Significant differences were found between the groups in bond strength (P < 0.001). Group M1 had the highest bond strength while Group L had the lowest bond strength. In terms of ΔE00 values, there were significant variations between the groups (P < 0.001). Group M1 had the highest colour stability, while Group M2 had the lowest colour stability. CONCLUSIONS The method of fabrication had an impact on the power of the bond between veneering ceramic and zirconia, as well as its colour stability. The restoration fabricated by a multilayer technique was cemented by resin cement (Rely X U200 Automix) which was found to be more resistant and colour stable. KEY WORDS Veneers, Heat-Press Technique, Bond Strength, Colour Different, Hydrothermal Aging.