## 2 Materials and Methods  
For the purpose of this research, a resin V-Print model was printed by SolFlex 650 * 350 3D printer (VCOO GmbH, Heidelberg, Germany). In place of tooth #35, we used a MIS standard internal hex implant analog, 3.75 mm/11.5 mm. Three scanning abutments were used (Figure 1):  
1. MIS scan abutment (titanium, two-piece), asymmetrical geometry, internal hex connection. 2. Alpha Bio (AB) scan abutment (PEEK and titanium, two-piece) cylindrical/asymmetric geometry, internal hex connection. 3. Zirkonzahn (ZZ) scan abutment (PEEK, one-piece), cylindrical/asymmetric geometry, internal hex connection. All scan abutments were screwed to the analog with electronic implant prosthetic screwdriver iSD900 (NSK\({}^{\circledR}\), Osaka, Japan) at 25 N.cm. Each of the three scan abutments were scanned with a TRIOS E2 (3 Shape\({}^{\circledR}\), Copenhagen, Denmark) laboratory desktop scanner, a QR file was created and then converted to STL file. This scanner and the resulting scans are considered the gold standard in terms of accuracy [17]. The in vitro intra-oral scans were performed with an Omnicam (CEREC\({}^{\circledR}\) AC Omnicam; Dentsply Sirona, Milford, DE, USA) scanner using the same scanning protocol suggested by Sirona. All scan abutments were scanned 30 times, and for each scan a STL file was created. The comparison between all the scans was conducted by digital software (PolyWorks\({}^{\circledR}\); InnovMetric, Quebec QC, Canada) using the best-fit method. This method constructedour alignment from surface points or edge points and used axial constraints to optimize the results. The various scan abutments have different geometries, yet all three have an internal cylinder, a flat occlusal surface and at least one flat side surface. Using these common characteristics, we have a basis for comparing these abutments. (Figure 2):  
1. Longitudinal axis of the scanning abutments is defined by the axis of the associated best-fitted cylinder to the abutment. 2. The point of intersection between the longitudinal axis and the best-fitted associated top surface of the scanning abutment is the center of the top (occlusional) surface. 3. The intersection between the top best-fitted (occlusional) surface and the best-fitted flat side surface is a straight edge. Based on this straight edge, we can calculate the angle of rotation of the scanning abutment (the angle of the scanning abutments relative to its longitudinal axis). For every type of scanning abutment, we have defined a system of axes that originates in the center of the upper surface. The X-axis is defined in the mesial-distal plane, where the positive inclination is distal. The Y-axis is defined in the buccal-lingual plane where  
Figure 1: Scan abutments from left to right: (**a**) Zirkonzahn (ZZ), (**b**) Alpha Bio (AB), and (**c**) MIS. Figure 2: (**a**) Illustrates the Alpha Bio pin scanned image. (**b**) Illustrates the key features of the scanning pin. Orange—the internal cylinder. Red—the longitudinal axis of the scan abutment. Purple dot—the center of the occlusal surface (blue). The intersection of the occlusal surface (blue) and the side surface (yellow) gives us the straight edge (green), used for calculating the angle of rotation. the positive inclination is lingual. The Z-axis is defined in the incisal-gingival plane, where the positive inclination is incisal (Figure 3). By using PolyWorks \(|\) Inspector\({}^{\text{TM}}\) Software Verification and Measurement, we superimposed (best-fit algorithm) each laboratory scan image with the intra-oral scan image, based on the adjacent teeth of the model's scanning abutments. The superimposition process allowed us to measure all the axes. Subsequently, we were able to extract the key features for each scanning abutment and calculate the spatial characterization of each scanning abutment relative to the reference as follows:  
1.