The effects of recasting on the cytotoxicity of dental base metal casting alloys

Abstract

Aim and Objectives: In dentistry, base metal casting alloys are extensively used for the fabrication of inlays, onlays, crowns, bridges, partial dentures, etc. During the casting of these alloys, excess amount of material used than needed will be collected as sprue buttons at the end, which is either added to the fresh alloy during casting and reused or disposed of. Materials and Methods: The aim of the present in vitro experimental study was to investigate the effect of the complete recasting of four commercially available cobalt-chromium (Co-Cr) and nickel-chromium (Ni-Cr) base metal casting alloys on their cytotoxicity. During the study, four groups of alloys were subjected to complete recasting up to twenty times without the addition of new alloy. The cytotoxicity assessment of the selected alloys after recasting (Co-Cr and Ni-Cr alloys) was carried out using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Results: The results indicated that Co-Cr alloys exhibit superior cell viability compared to Ni-Cr alloys, and cytotoxic potential of the alloys increased with repeated casting and led to increased cell death. The recasting of alloys in the present study did not show high cytotoxicity even after the 20 th recasting. Conclusion: From the results of the present study, it can be concluded that the alloys generated as a waste in the dental laboratory can be safely reused up to five times or at least once before they can be disposed, which reduces the cost of the treatment and also helps in conserving the natural resources.

Comparative in-vitro microscopic evaluation of vertical marginal discrepancy, microhardness, and surface roughness of nickel–chromium in new and recast alloy

“…Wagner et al 21 calculated the physical characteristics of base metal alloys and suggested that they can be used for four generations without significant variation. Nandishet al 22 confirmed that there was no significant deterioration in Ni–Cr alloy recasting for up to 10 generations, and that mixing used metal with new metal and recasting 100 times did not create significant deteriorating changes in the base materials, microstructure, or clinical quality. The authors stressed the importance of adhering to uncontaminated materials to reduce pollution and negative impacts on the material.…”

Cytotoxicity of Commercially Pure Titanium (cpTi), Silver-Palladium (Ag-Pd), and Nickel-Chromium (Ni-Cr) Alloys Commonly Used in the Fabrication of Dental Prosthetic Restorations

“…In the case of the Ni-Cr cytotoxicity, other studies found that Ni ions released from Ni-Cr alloy exhibited the highest cytotoxic effect and this was referred to the high percentage of nickel in Ni-Cr alloy, unlike the Co-Cr alloys that exhibit passivity feature by forming oxide layer of chromium reducing the corrosion behavior. This toxicity level was enhanced by repeated times of alloy recasting [ 24 ]. In addition, the formation of the NiO layer on the alloy enhances Ni ions dissolution, especially at an acidic pH, causing it to be more corrosive [ 10 , 14 ].…”

Experimental Study Regarding the Behavior at Different pH of Two Types of Co-Cr Alloys Used for Prosthetic Restorations

“…Because elements as Co, Cr, and Mo are considered less toxic than Ni and are released at much lower concentrations, the Co-Cr-Mo alloys are preferred, compared to Ni-Cr-based alloys, due to their enhanced biocompatibility and higher corrosion resistance [ 44 , 45 ].…”