Influence of recast NiCrMo alloy addition on porcelain-fused-to-metal bond strength

Abstract

The recasting of dental metal alloys can change the chemical composition of fabricated casts, which ultimately affects the properties of a dental component. The purpose of this study was to assess the effect of adding a recast material on the bond strength between dental porcelain and NiCrMo substrate. The research used a dental alloy NiCrMo with a trade name Remanium CS+. Three groups of the dental alloy were prepared by alloying 50% of brand-new alloy with alloy remnants from previous castings. The specimens in the first casting group used 100% new alloy and served as a control group (C1). The second group consisted of equal amounts of new alloy and alloy remnants after single-casting (C2). The third group contained 50% of new alloy and alloy material that was cast twice (C3). The chemical composition of cast samples was examined by emission spectrometry. The structure of both the metal substrate and porcelain fused-to-metal bonding were investigated with scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Hardness was measured with a Vickers microhardness tester. The metal–ceramic bond strength was investigated according to the ISO 9693 standard, and fractography analysis was performed by the SEM method. The influence of NiCrMo alloy recasting on hardness and bond strength results were additionally tested statistically. Results indicate that casts fabricated by recasting NiCrMo alloy obtained favourable results of metal-ceramics bond strength. A brand-new metal alloy should be used in the casting of dentures, however if subjected to recasting, it should be melted with the addition of 50% of previously non-cast metal.