Purpose: The additive technologies characterize with building of one layer at a time from a powder or liquid that is bonded by means of melting, fusing or polymerization. The methods, mostly used in dentistry, include selective laser sintering, selective laser melting and 3D printing. The aim of the present paper is to investigate the microstructure and hardness of fixed dental prostheses produced by three different technologies. Design/methodology/approach: Four-part dental bridges were manufactured of Co-Cr alloy by standard lost-wax process, casting of 3D printed wax models and Selective Laser Melting (SLM). The microstructure was investigated by optical microscopy and SEM. EDX and EPMA analyses and Vickers microhardness measurements was done. Findings: It was established that the microstructure of cast samples is dense, inhomogeneous, consisting of large grains with dendrite morphology, while the microstructure of the SLM bridges is porous. Pores, elongated along the direction of the melted layers were observed. The microhardness investigations showed highest average hardness of the samples, produced by SLM (356HV-407HV), followed by the hardness of the samples, cast by 3D printed models (327HV-343HV) and these, manufactured by standard lost-wax process (251HV-274HV). The measurements along depth of the samples showed nearly even microhardness distribution in the bridges, produced by SLM, and fluctuations of the microhardness values along the depth of the cast bridges due to the inhomogeneous microstructure. Research limitations/implications: As the additive technologies for production of dental restorations from wax, polymers and metal alloys are developed last years, additional investigations are needed for development of more precise technological regimes. Originality/value: The comparison between the microstructure and hardness of dental prostheses made by lost-wax process and SLM reveals the peculiarities of the constructions produced by new technology.
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