Shear Bond Strength: Function of Zirconia, Surface Treatment and Cement
Objectives: The objectives of the study are to measure and compare in vitro shear bond strength as a function of: (A) Zirconia restorative materials - Tetragonal (IPS e.max® ZirCAD LT)/LT and Hybrid (IPS e.max® ZirCAD MT)/MT. (B) Luting Cements – Self-adhesive (SpeedCEM® Plus (Transparent))/SP and adhesive (Variolink® Esthetic DC (Neutral))/VE. (C) Surface Treatment – With and without MDP containing restorative primer application (Monobond® Plus)/MP. Methods: Zirconia discs (LT/MT) were sectioned, mounted and ground to a flat surface (320/400/600 grid SiC polishing paper) and micro-etched (Al2O3/50 μm/15 psi). Specimens (n=10) were randomly divided into six experimental groups (Table 1).
The application of MDP containing restorative primer with VE is per manufacturer's instructions. Pre-cured resin composite (Tetric® EvoCeram/(A2)) rods (RCR)/(Diameter-2.38mm) were sand-abraded (Al2O3/50 μm/15 psi), adhesive (Adhese® Universal) was applied and light cured (10 seconds). The RCR were cemented to restorative substrates per table-1 and light cured following manufacturer's recommendations under constant load (113.40 grams). Specimens were stored in an incubator for 24 hours (37°C/100% humidity) and shear bond strength was measured (Instron Universal Testing Machine/crosshead speed-1.0 mm/min). The fractured surfaces of each specimen were evaluated under light microscope (30X). Data was analyzed by one-way ANOVA and Tukey’s HSD post-hoc test (α=0.05). Results: Shear bond strengths (Mean±SD)/(MPa) were obtained (Table 2). Similar superscripts showed no significant difference. Conclusions: Within the limitation of the study, no significant differences in shear bond strength with tested restorative materials and luting cements were observed. The application of ceramic restorative primer significantly increases the bond strength with adhesive resin cement.