## 2 Materials and Methods  
A scannable gypsum cast covered with pink gingiva used as the reference model (RM) was a representative of a fully dedentulous maxilla with four implant analogs (RC Bone Level Implant Analog; Institut Straumann AG) located in right first premolar (RP), right lateral incisor (RLI), left first premolar (LFP), and left lateral incisor (LLI) regions demonstrating a typical clinical scenario. The two anterior analogs were parallel whereas those posteriorly situated were of 17 degrees angulation. This cast was obtained from an all-on-four acrylic model by taking a polyether (Impregum Polyether Impression Material; 3M ESPE, Seefeld, Germany) impression with splinted implant level impression copings (Implant level open tray impression post, D4.6 mm, Straumann, Basel, Switzerland). Autopolymerizing pattern resin (Pattern Resin LS; GC) was used to join the copings where it was sectioned and rejoined after 24 h of setting to minimize the resin polymerization shrinkage [40]. Light pink impression silicone (Gingifast Rigid; [PERSON], Badia Polisine, Italy) was first placed surrounding the impression copings to create the gingival mask. Then scannable plaster (CAM-Stone N; SILADENT, Goslar, Germany) was mixed according to the manufacturer's instructions and poured over the impression. To create control Standard Tessellation Language (STL) files for trueness comparison, new identical four implant level ISBs (Cares Mono Scanbody D4.6 mm PEEK/TAN, Institut Straumann A/S, Basel, Switzerland) of the same diameter and height were chosen and prior to tightening, the pink silicone was covered with scanning powder. After that they were tightened at 15 N over the gypsum model and digitized with a desktop scanner (E3; 3 Shape A/S, Copenhagen, Denmark) of 7 um accuracy. This file was considered as a baseline scan acting as a standard to which all other scans would be compared. On the part of the DIOS group, fifteen scans were obtained using a previously calibrated IOS (TRIOS3 Cart; 3 Shape A/S) after tightening implant level scan bodies (Cares Mono Scanbody D4.6 mm PEEK/TAN, Institut Straumann A/S) on the RM (Figure 1). To escape the impending adverse effects of practitioner fatigue, a 5-min break was scheduled between scans. The progress of the scanning strategy used was slow and constant where the practitioner started from the occlusal surface, continued to capture the buccal region, and then ended by registering the palatal area starting from the scan body of implant LFP and ending at that of implant RFP. The operator tried to capture all the details of each ISB, without asserting too much on them from the same angle, to prevent unnecessary reflection. All scans were captured in the same environmental conditions with ambient light of 1003 lux, without interference from any external light sources [16; 17]. For the DPG group, implant level Pic transfers (PiCabutment; PiC dental, Miami, FL, USA) were screwed on top of the analogs (Figures 2 and 3). A stereo-camera positioned 15-30 cm away from the reference cast with a supreme angle of 45 degrees with respect to the transfers was used to register implant positions (PiC camera; PiC dental). After defining the code of each Pic transfer, the information was captured and processed by a customized Pic program (Pic Cam Soft v1.1; PiC dental) that created vectors representing the implants' positions. From the Pic library file, ISBs having the same shape as the ones used for the RM were chosen to replace the vectors, and STL files were exported. Fifteen STL files were attained for this group. Figure 1: Implant level intraoral scan bodies tightened on the reference model. After all scans were captured, the reference file and the scans obtained from the DIOS group were trimmed using reverse engineering software (Geomagic Control X; 3D System, Boston, MA, USA) leaving the scan bodies only and disregarding the surrounding structures.