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. Lightcuring 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.

A Comparison of Microtensile Bond Strength, Film Thickness, and Microhardness of Photo-Polymerized Luting Composites

“…Grandio Blocks was reported to have higher absorption coefficient, with higher light penetration before being absorbed, which facilitates the entire photo-polymerization of the photo-polymerized composite [35]. It has been suggested that the use of photo-polymerized composites to bond CAD/CAM materials could be an alternative to the dual-cured resin cements [24,[43][44][45]. By increasing the thickness of luting materials, the chance of incorporation of voids within the cured cement layer is expected to be high [46].…”

“…The microhardness and the degree of conversion also showed controversial results, which depended on the resin composite material [21][22][23]. This was shown to be dependent on the number of the pre-heating cycles [24] and the original viscosities of the photo-polymerized composites [18].…”

“…It was noticed that pre-heating time of photo-polymerized composites varied from study to study depending on the pre-heating method [20,[23][24][25][26]. It is not clear whether pre-heating of different photo-polymerized resin composites can substitute the dual-cured resin cement to bond CAD/CAM resin composite with different thicknesses.…”