## 2 Materials and Methods
If a single examiner had performed all the scans, it could be assumed that the knowledge gained in scanning over the long period from 2012 to 2021 had an influence on the results. The analyses were based on evaluation methods already known and used in a previous study [26]; for this purpose, all scan data were first exported to a standard STL file format. For conventional impressions (\(n=10\)), the open-tray technique was used [30; 31]. A custom may consisting of C-Plast (Candulor Dental GmbH, Rielasingen-Worblingen, Germany; thickness 3 mm) with a tubular design around the impression copings (including RCs) was fabricated. Four impression copings (N TR-RN024.8, nt-trading, Karlsruhe, Germany) were fixed into the implants (15 Ncm). To compensate for the laboratory conditions, the impression material (Impregum Penta) was allowed to set for ten minutes (23 \(\pm\) 1 \({}^{\circ}\)C temperature, 50 \(\pm\) 10% relative humidity). Afterwards, impression post screws were loosened, and the impression was removed from the IMM. A total of ten impressions were obtained. Laboratory analogs were repositioned on the impression posts (N51, nt-trading, Karlsruhe, Germany) and tightened with a torque of 15 Ncm. Using Fujirock EP (GC Corporation, Tokyo, Japan), ten plaster casts were produced and stored under laboratory conditions for seven days. The received STL files were imported into Gom Inspect (Gom, Braunschweig, Germany) and aligned to the reference file with the RCs to measure the digital impressions. This made it possible to superimpose the respective coordinate systems within the digital impressions using the reference cuboids. To clearly determine the distances within the digital models, the distances between the reference cuboid and the implant-abutment interface points (IAIPs) were measured in the IMM. This procedure was applied to both the digital and the conventional models. Then, the absolute linear displacement (\(\Delta\)R) of the IAIPs for each implant position from the digital and conventional impressions and the reference data set was calculated using \(\Delta\)R = \(\sqrt[2]{(x_{2}-x_{1})2+(y_{2}-y_{1})2+(z_{2}-z_{1})2}\). To measure the deviations of rotation and angulation, planes and cylinders were constructed at the respective scan bodies. This made it possible to compare the same planes and cylinders in \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Scanner Family** & **Type** & **Software Version** & **Release Date** & **Label** \\ \hline \multirow{4}{*}{\begin{tabular}{c} **True Definition** \\ **Scanner** \\ \end{tabular} } & True Definition scanner (Cart version) & 4.0.3 & 2013-04 & TD\_4.1 \\ \cline{2-5}  & True Definition scanner (Cart version) & 5.4 & 2018-07 & TD\_5.4 \\ \cline{2-5}  & True Definition scanner (Portable version) & 5.4 & 2018-07 & TDpb\_5.4 \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} **TRIOS** \\ \end{tabular} } & TRIOS II & 2013-01 & 2013-01 & TR2 \\ \cline{2-5}  & TRIOS 4 & 19.2.4 & 2020-12 & TR4 \\ \hline \multirow{4}{*}{
\begin{tabular}{c} **CEREC** \\ \end{tabular} } & CEREC Omnicam & 4.2.1.61068 & 2012-04 & OC\_4.2 \\ \cline{2-5}  & CEREC Omnicam & 4.6.1.152739 & 2018-05 & OC\_4.6 \\ \cline{1-1} \cline{2-5}  & CEREC Primescan & 5.1.0.190461 & 2020-05 & PS \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Intraoral scanning systems with corresponding software versions used in the present study. the master model and digital models. The corresponding distances and angles are shown in Figure 2.  
To measure the IAIPs, rotation, and angulation of the gypsum models, four scan bodies (N1410, Medentika, Hugelsheim, Germany) were tightened in the implants with a torque of 15 Ncm and measured using a CMM (RAPID, Thome, Messel, Germany) to evaluate the absolute 3D distances between the IAIPs and RC. To avoid errors that can result from even the smallest vibrations of the CMM due to manual manipulations and to increase the precision of the measurements, the following measures were taken.