# Surface Analysis of 3D (SLM) Co-Cr-W Dental Metallic Materials
## 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 [PERSON] [1, 2, 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 replacement 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]. Additive manufacturing (AM) was initially performed and developed in the 1980s as a new technique to improve the classical technologies for obtaining materials. In the case of metallic materials, the main property of these techniques (stereo-lithography, fused deposition model, selective electron beam melting, selective laser sintering, selective laser melting, and ink-jet printing) is based on the realization of one layer (different thicknesses) on top of another using a powder. The layers are connected through melting or fusing [6; 7]. Based on the definition given by ASTM, the process of AM represents obtaining, layer by layer, metallic elements from a 3D design project as a bottom-top technique of making an element in a different way from the usual approach of melting [8; 9; 10]. From the different methods of obtaining dental materials based on Co-Cr-W (the tungsten element in Co-Cr alloy ensures increased tensile strength, increased hardness of alloys, and better resistance to corrosion and electro-corrosion [11; 12; 13]), additive manufacturing using selective laser melting equipment presents very good mechanical behavior [14]. The 3D printing of medical elements can address many of the specific difficulties in obtaining materials with special characteristics in the medical field, such as special structures of different thicknesses and, most importantly, 3D structures. Their surfaces after this CAD design process, at present, still require advanced surface processing, solutions for which are wanted at the industrial (mechanical or chemical) and laboratory (e.g., laser modifications of the surface) levels. In the field of dentistry, the condition of the surface of metallic elements is very important for the activity undertaken in the oral environment in terms of the interaction between the metallic contact surface and the environment of existing biological solutions. The loss of dental material is higher in the case of higher surface exposure to a liquid. Among other reasons, the condition of the final surface of metallic materials for dentistry applications is important.