## 1 Introduction  
Casting alloys have been an important part of prosthodontic treatment for more than a century [1]. Initially, gold alloys were preferred for this purpose because of their biocompatibility and ease of use. As the price of gold increased substantially, manufacturers focused on less expensive alternatives such as Au-Ag-Pd and Pd-Ag alloys [2], followed by non-precious-metal dental alloys, such as the Fe-Cr-Ni, Ni-Cr, Co-Cr, and Ti alloys. Because of the allergenic potential of Ni-based alloys, currently, Co-Cr dental alloys are most commonly used for dental applications [3]. Co-Cr alloys are biocompatible materials, with high strength, good wear resistance, fatigue resistance, and corrosion resistance, along with a relatively affordable price; they are suitable for crown and bridge substructures, partial skeletal denture frameworks, and implants. Other elements are frequently added to improve the mechanical properties of the material, for example, Mo and W, which contribute to solid solution strengthening [4]. Co-Cr alloys are rather difficult to process using a traditional casting technique because of the manual manufacturing steps involved, leading to potentially low accuracy and satisfactory quality. Computer-aided design and computer-aided manufacturing (CAD/CAM), either subtractive or additive, offers the possibility of overcoming the disadvantages of the casting process [5; 6; 7]. The subtractive CAD/CAM technique used for dental applications allows the software-controlled mechanical milling of material blanks in order to obtain parts of a certain geometry [8]. Because the blanks are produced under high industrial standards, this reduces any flaws and pores, compared to the traditional manufacturing methods [9]. The subtractive method has the advantage of using homogenous materials, but its major drawbacks result from material loss and high costs. In order to overcome these disadvantages, additive CAD/CAM procedures have been introduced. Also known as 3D printing, this process addresses the drawbacks of subtractive manufacturing in the CAM step. In this case, the prosthetic appliances are fabricated by layering the materials, instead of milling, and this process enables the manufacture of polymeric materials and alloys, as well as ceramics [10]. When considering the 3D printing of dental alloys, the most widely used technologies employ powder bed fusion (PBF): selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM) [11], which share common basic principles. They involve a heat source that is used to consolidate the metallic powder, forming a 3D object by means of layer-by-layer deposition according to a CAD file, using a printer. Nevertheless, each technology has unique and special features, characteristics, capabilities, and limitations [12]. In SLS, the process consists of melting the edges of the grains, while in SLM and EBM, the metal powder is fully melted. Different modalities are used to achieve the melting point [9]. SLS uses a high-power laser to fuse small particles of the powder-form material, heated just below the melting point. As the laser beam moves, the material is being solidified. After each layer's solidification, the powder bed is lowered by one layer of thickness, and the emerging empty space is filled with new powder material; this process is repeated until completion [12; 13]. Unfortunately, parts fabricated by SLS are characterized by poor surface quality and high porosity [14]. SLM aims to produce highly dense objects using CO\({}_{2}\) or fiber lasers (Nd:YAG or Yb:YAG) [15]. In SLM, the raw powder material is fully melted by the laser beam, resulting in selective melt pools, which, after re-solidification, turn into fully dense parts (>99% density, compared to 70% in SLS). The melting process can be adjusted by varying the wavelength, laser source, and power. Nevertheless, SLM production suffers from melt pool instabilities, which may lead to defects and imperfections such as surface roughness and the risk of internal porosity [9].