Microstructure and Mechanical Properties of Co-Cr Alloy Fabricated by Selective Laser Melting Technology for Removable Partial Denture Frameworks

The present in vitro study aims at evaluating the suitability and the reliability of the selective laser melting (SLM) technique for constructing removable partial denture frameworks (RPDs). Ten (n = 10) specimens of Co-Cr alloy, with dimensions according to the ISO 22674 “Dentistry–Metallic materials for fixed and RPD restorations and appliances,” were designed by CAD software and fabricated in an SLM machine. The porosity of the produced Co-Cr specimens was evaluated using x-ray scans. Microstructural and crystallographic analyses of the studied materials were performed by SEM observation, EDS elemental analysis, and x-ray diffraction. Measurements of mechanical properties (i.e., ultimate tensile strength, 0.2% yield strength, elongation, Young’s modulus, and Vickers microhardness) were conducted according to the ISO 22674 specification. The SLM technique fabricated dense Co-Cr specimens, consisting of the γ-fcc and ε-hcp cobalt phases. The values of the ultimate tensile strength, 0.2% yield strength, elongation, Young’s modulus, and Vickers microhardness were 1065.8 ± 27.18 MPa, 695.11 ± 54.74 MPa, 9.88 ± 1.08%, 279.27 ± 32.75 GPa, and 4.95 ± 0.60 GPa, respectively. According to the ISO 22674 specification, which classifies the metallic dental restorative materials according to their mechanical properties, the experimental results qualify SLM as a reliable technique for fabricating RPDs, since the mechanical properties of the produced specimens, reported above, are higher than the minimum values required by the ISO 22674 to produce RPDs.