## 2 Materials and Methods  
Straumann BLX 4.0 mm \(\times\) 12 mm implants (Institut Straumann AG, Basel, Switzerland) and the corresponding screw-retained abutments (SRAs) (Institut Straumann AG, Basel, Switzerland) were placed in three defendulous acrylic mandible models with artificial gingiva (Figure 1). Each reference model presents a different implant distribution, according to the Carames Classification I (CCI)--option A with 6 implants (2 implants in the position of the lateral incisors, 2 anterior to the mental foramen, and 2 in the region of the first molars); option B with 4 implants (2 implants in the position of the canines and 2 in the region of the first molars); and option C with 4 implants (2 implants in the position of the lateral incisors and 2 anterior to the mental foramen) [27]. For the models used in this study, the distance between the implants was approximately 10 mm in CCI options A and C, whereas in CCI option B, it increased to approximately 16 mm. For digital impressions with IOs, scanbodies (CARES Mono scanbodies, Straumann AG, Basel, Switzerland) were screwed at 10 Ncm into the SRA (Figure 2a). For digital impressions with photogrammetry, PIC transfers (PIC system, Madrid, Spain) were used, also with a tightening of 10 Ncm (Figure 2b). Subsequently, a total of 90 digital impressions were taken, 30 for each of the 3 different implant distributions mentioned: 10 with an IO Trios 3 scanner (3 Shape, Copenhagen, Denmark), 10 with an IO Mediti 500 scanner (Medit corp., Seoul, Republic of Korea), and 10 using photogrammetry technology performed with a PIC Dental scanner (PIC system, Madrid, Spain) (Figure 3) [22]. This sample size is supported by similar studies available in the literature; therefore, no statistical power analysis was performed [22; 28; 29]. Figure 1: Analog mandibular model with implants and screw-retained straight abutments ([PERSON], Switzerland). Figure 2: Preparation of analog models for digital impression: (**a**) analog model with scanbodies ([PERSON], Switzerland); (**b**) analog model with PIC transfers (PIC Dental, Spain). The scanners were calibrated prior to each scan, following the manufacturer's instructions, and subject to the same room conditions. The three reference models were digitized in a controlled environment, with a temperature of 20 \(\pm\) 1 \({}^{\circ}\)C, a relative humidity of 50 \(\pm\) 20%, and an illuminance of approximately 1000 lux. The digital impressions were performed by a single operator and saved in the Standard Tessellation Language (STL) format. The STL files were subsequently imported into computer-aided design software (Exocad DentalCAD 3.2 Elefsina, exocad GmbH, Darmstadt, Germany) to generate the digital replicas. After identifying the scanbodies using the library, the replicas were automatically positioned and exported as STL files. The aforementioned STL files with the spatial position of the replicas were imported into the metrology software for three-dimensional analysis (Geomagic Control X 2022.0.1, 3D Systems, Rock Hill, SC, USA) [29]. In the present study, precision refers to the reproducibility of the digital impression measurements, and it was determined by successively overlapping the impressions obtained with the IOs and photogrammetry technology. The STL files from each group were compared to one another using the root mean square (RMS) values, as described by [PERSON] et al. [22]. A total of 45 comparisons were made per group under study (Table 1). For all comparisons, the \"initial alignment\" tool was selected followed by the \"best-fit alignment\". Subsequently, using the \"3D compare\" tool, the discrepancies between the superimpositions were quantified. File alignment was defined with a tolerance of best values between +30 and \(-\)30 \(\upmu\)m (Figure 4). Precision was assessed based on RMS values of 3D comparisons in micrometers (\(\upmu\)m) and the data obtained are presented as means \(\pm\) CI at 95%.