## 2 Materials and Methods  
The study evaluated marginal and internal discrepancies of metal-ceramic crowns with cobalt-chromium frameworks obtained by the conventional casting of printed resin patterns, SLS, SLM, and CAD/CAM milling. Framework design was a \"cut-back,\" and it was the same for all samples. All restorations were made for a resin molar. The marginal and internal fit evaluation was evaluated using the non-destructive method, silicon replica technique, before and after ceramic over pressing. Silicon replicas were sectioned and photographed under the microscope with 20\(\times\) magnification, and images were analyzed using image processing software (Figure 1). The measurements were performed in nine points divided as follows: marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), axio-oclusal angle (AOG), and occlusal wall at internal gap (OG) (Figure 2). Silicon replica technique was used to measure the space between the tooth and the framework. The resulting data were statistically analyzed. A resin first upper molar was reduced for a full-coverage ceramic fused to metal crown with a 1 mm chamfer shoulder, tapered of axial walls of 6\({}^{\circ}\) and a 1.5 mm occlusal reduction, with beveled support cusps. The prepared tooth was replicated after silicon impression (Fegurasil AD Special, Feguramed, Germany), and resin models have been obtained using a provisional restorations resin (Structur 3, Voco, Cuxhaven, Germany). The resin was chosen to simulate the tooth as it has similar mechanical properties to natural dentine tissue. These abutments have been divided into four groups. Two groups, forty-eight prepared teeth, were scanned with D700 3D Scanner (3 Shape, Copenhagen, Denmark) to produce laser-sintered copings (SLS) (\(n=24\)) and cast copings (T) (\(n=24\)). 3 Shape software was used to create the cut-down design, to obtain a uniform porcelain veneering thickness (Figure 3). Twenty-four frameworks were fabricated by selective laser sintering (SLS) (PXS Dental, Phenix Systems, Riom, France) using cobalt-chromium dental alloy powder (Starbond CoS Powder 16, S&S Sheftner GmbH, Mainz, Germany). The powder layer was of 30 \(\upmu\)m, with a compaction rate of 30%, in the controlled atmosphere of N2 with a gas flow of 5 L/min, using a Class 1 laser with a wavelength of 1070 nm and 50 W power. Twenty-four patterns were printed from castable-resin to fabricate the casted group (E-Partial Press-E-Cast, EnvisionTEC, Dearborn, Michigan, MI, USA) using Perfactory 4 Digital Printer P4 DDP (EnvisionTEC, Dearborn, Michigan, MI, USA) (Figure 4) to eliminate operator-induced flows. After printing, patterns were removed from the printer, cleaned by immersing in pure Isopropyl alcohol with 99%, dried and processed by further photopolymerization in the Otoflash unit (EnvisionTEC, Dearborn, Michigan, MI, USA) according to manufacturer instructions. Figure 1: Measurements of silicon replica with ImageJ software (NIH, Bethesda, MA, USA). Figure 2: Measurement points. Patterns were prepared for casting, invested (Bellavest SH, BEGO, Bremen, Germany), and cast with a cobalt-chromium alloy, Wirobond 280 (BEGO, Bremen, Germany), by negative-pressure casting (Nautilus, Bego, Bremen, Germany). Frameworks were divested (Figure 5), cleaned with airborne particles (200 \(\upmu\)m, and 75 \(\upmu\)m), and prepared for veneering. Figure 4: 3D resin patterns for casted frameworks. Figure 5: Divested cast samples. Figure 3: Framework design. An oxide firing was performed. The other group of forty-eight abutments was scanned with Dental Wings 7 Series Scanner (Dental Wings INC., Montreal, QC, Canada) for milled (F) (\(n=24\)) and selective laser melted (SLM) (\(n=24\)) copings. An anatomic-reduced framework design has been made using DWOS software (Dental Wings INC., Montreal, QC, Canada) using the same parameters used for the other two groups.