Characterization of alloys produced with new system for processing dental prosthesis

Removable partial dentures (RPD) are traditionally made of casted alloys using the lostwax technique. Laser-sintering is a new additive manufacturing technique for processing RPD metal frameworks that can produce RPDs frameworks quickly with high precision and at low cost. The objective of this study was to characterize the mechanical, crystallographic, and biocompatibility properties of RPD Cobalt-Chromium (Co-Cr) alloy processed by laser-sintering technique and compare them to those of conventional casted Co-Cr alloy. Methods: Co–Cr samples were fabricated by either conventional casted (CC) or laser-sintering (LS) technique. The mechanical and physical properties of the alloys (i.e. strength, elastic modulus, fatigue behaviour, microhardness, crystallography, and porosity) were evaluated using three-point bending test, Vickers hardness measurements, X-ray diffraction (XRD), Pycnometry, micro–computed tomography (micro-CT), and Scanning Electron Microscopy (SEM). The releases of toxic metal ions from Co-Cr alloys was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The alloys biocompatibility was assessed by Alamar Blue viability assay and cytotoxicity lactate-dehydrogenase (LDH) assay on human epithelial cells. Results: LS alloy showed higher rigidity, porosity, and fatigue resistance compared to CC alloy (p<0.05). Both materials had similar flexural strength, micro-hardness, and biocompatibility (p>0.05). The toxic ion release and biocompatibility assay reveled that both groups had similar behaviour. Conclusion: Both laser-sintered and conventional casted Co-Cr alloys are biocompatible; however, lasersintered Co-Cr alloys are more precise and present better fatigue resistance than casted alloys. Accordingly, it could be anticipated that laser-sintered RPD could presents clinical benefits over casted ones in term of fitting and mechanical stability.