Effect of Preheating Cycles on Microshear Bond Strength of Nanohybrid Resin Composite Luted to CAD/CAM Ceramic

Abstract

Objective: This study aimed to investigate the microshear bond strength of adhesive resin cement to Leucite-reinforced CAD/CAM ceramic and compare it with that of prewarmed nanohybrid resin composite. Materials and methods: Sixty Empress CAD ceramic plates were prepared. Each ceramic plate received five Tygon tube micro-cylinders filled with bonding agents creating 5 resinous micro-cylinders on each ceramic plate. In the first group (GpA), they were filled with resin cement, nanohybrid resin composite as a bonding agent was applied in the second group (GpB), after warming at 50℃, in the third group (GpC), two prewarming cycles were performed. Light-curing for 20seconds was applied. Micro-shear bond strength testing (μSBS) was performed using universal testing machine with a crosshead speed of 1 mm/min until failure occurred. The μSBS was calculated in MPa by dividing the load (Newton) over the respective surface area (mm 2 ).Data were tabulated and analyzed and showed normal distribution when checked using Kolmogorov–Smirnov test. One-way ANOVA used to compare between the tested groups for μSBS data followed by Tukey HSD post-hoc test for pairwise comparisons. Significant level was set at 5% (α=0.05). Results: One- way ANOVA showed a significant difference between tested groups (p < 0.001). Where heated composite (two prewarming cycle) showed the highest mSBS compared to other groups (p < 0.05). Nevertheless, heated composite (one prewarming cycle) showed an improved μSBS compared to resin cement group, but the increase was insignificant (p=0.081). Conclusion: pre-heated nanohybrid resin composites seem to be a potential alternative to resin cement to lute ceramic restorations.