applied sciences Article Surface Analysis of 3D (SLM) Co–Cr–W Dental Metallic Materials Elena-Raluca Baciu 1 , Ramona Cimpoes , u 2 , Anca Vit , alariu 1, *, Constantin Baciu 2 , Nicanor Cimpoes , u 2, *, Alina Sodor 1 , Georgeta Zegan 1 and Alice Murariu 1   Citation: Baciu, E.-R.; Cimpoes , u, R.; Vit , alariu, A.; Baciu, C.; Cimpoes , u, N.; Sodor, A.; Zegan, G.; Murariu, A. Surface Analysis of 3D (SLM) Co–Cr–W Dental Metallic Materials. Appl. Sci. 2021, 11, 255. https://doi.org/ 10.3390/app11010255 Received: 24 November 2020 Accepted: 25 December 2020 Published: 29 December 2020 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional clai- ms in published maps and institutio- nal affiliations. Copyright: © 2020 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Faculty of Dental Medicine, “Grigore T. Popa” University of Medicine and Pharmacy, 700115 Iasi, Romania; elena.baciu@umfiasi.ro (E.-R.B.); alinasodor@yahoo.com (A.S.); georgeta.zegan@umfiasi.ro (G.Z.); alice.murariu@umfiasi.ro (A.M.) 2 Faculty of Materials Science and Engineering, “Gh. Asachi” Technical University, 700259 Iasi, Romania; ramona.cimpoesu@tuiasi.ro (R.C.); constantin.baciu@tuiasi.ro (C.B.) * Correspondence: anca.vitalariu@umfiasi.ro (A.V.); nicanor.cimpoesu@tuiasi.ro (N.C.) Featured Application: Specific prototyping of dental metal crowns and medical implants. Abstract: The surface condition of the materials involved in dentistry is significant for the subsequent operations that are applied in oral cavity. Samples of Co–Cr–W alloy, obtained through selective laser melting (SLM) 3D printing, with different surface states were analyzed. Surface analysis after the 3D printing process and sandblasting was realized from microstructural, chemical composition, profilometry, droplet adhesion, scratch test, and microhardness perspectives. The results presented a hardening process and a roughness modification following the sandblasting procedure, a better adhesion of the liquid droplets, the appearance of micro-cracks during the scratch test, and the oxidation of the sample after the 3D printing process and surface processing. Keywords: 3D printing; Co–Cr–W; dental materials; SEM; EDS; scratch test; droplet adhesion; profilometry; microhardness 1. Introduction Characterized by a remarkable biocompatibility, cobalt-based alloys are widely used in the manufacturing of implants for the hip and knee, elements for immobilizing bone fractures (screws, plates, nails, etc.), and heart valves, and they have numerous applications in dentistry. These alloys can be: Binary (Co–Cr), ternary (Co–Cr–Mo and Co–Cr–Ni) or complex, with a content of approximately 65% Co, 30% Cr, and other elements (W, Ni, Ti, Nb, Si, etc.) in proportions of a maximum of 5%. These alloys belong to the category of stellites (lat. Stella = star), because they are characterized by a metallic luster persistent over time. They were originally produced by Deloro Stellite Company (Kokomo, IN, USA), based on the 1881 invention of Elwood Haynes [1–3]. Metal-based biomaterials are extremely important for improving and increasing the impact of implantable devices. Their applications mainly include load-bearing implants (e.g., metallic joints, such as hip), elements for stabilization, clips, wires, needles, plates, and screws, and a special category of dental implants and metal crowns proposed for the rehabilitation of deteriorated bone structure. Metal elements with applications in the field of medicine can be used as replace- ment elements for deteriorated tissues and in the recovery of soft tissues such blood vessels. The most commonly used metallic biomaterials are based on stainless steels, Co–Cr alloys, and Ti-based alloys. A new class of metal-based materials are biodegradable alloys, such as Mg-, Fe-, and Zn-based alloys. This special class can largely benefit from 3D printing technologies. Other examples of the alloys used in medical field are based on Ta, Nb, and noble materials such as Au- and Ag-based alloys with high percentages of Pt and Au. These materials are typically applied for the realization of dental prostheses such as crowns, dentures, inlays, and bridges [4,5]. Appl. Sci. 2021, 11, 255. https://doi.org/10.3390/app11010255 https://www.mdpi.com/journal/applsci