Bonding Indirect Resin Composites to Metal: Part 2. Effect of Alloy Surface Treatment on Elemental Composition of Alloy and Bond Strength

Purpose: This laboratory study compared the effect of different surface treatments of amedium-gold, high-noble alloy on the shear bond strength of an indirect, highly filled resincomposite to the alloy and on the elemental composition of the alloy surface. Materials and Methods: Ninety disks, cast in a medium-gold, high-noble porcelain-fused-to-metal alloy (VDeltaloy), received three different surface treatments: sandblasting with 50-µm Al2O3 (group1) or 250-µm Al2O3 (group 2) and chemical agents, or with 250-µm Al2O3 without chemicalagents (group 3) prior to bonding of an indirect resin composite (Artglass, and chemicalagents Siloc-pre and Siloc-bond). The specimens were tested in shear, half of them after 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37°C and thermocycling (2,500 cycles between 5 and 55°C). Morphologic and qualitative changes on the alloy surface after sandblasting with 50- or 250-µm Al2O3 weree xamined by SEM using EDS analysis and compared with polished specimens. Statistical analysis was performed using two-factor ANOVA. Results: The mean shear bond strengths (in MPa) after dry or wet storage and thermocycling were 29 and 24 for group 1, 21 and 18for group 2, and 17 and 12 for group 3, respectively; there was a statistically significant difference among the groups. Sandblasting of the alloy surface led to statistically significant changes in elemental composition. These changes were of greater magnitude when 50-µmAl2O3 particles were used. Conclusion: The particle size used for sandblasting influences the shear bond strength between a high-noble alloy and a highly filled indirect resin composite,as well as the elemental composition of the alloy surface.