## 4 Discussion
As previously described, and in accordance with ISO definitions, \"accuracy\" represents the combination of \"trueness\" and \"precision\", where \"trueness\" refers to the ability of an impression to reproduce the dental arch as reliably as possible and without distortions, whereas \"precision\" (repeatability) refers to the degree of agreement among repeated impressions obtained under similar conditions [21; 23; 30; 41; 42]. In the present investigation, only \"trueness\" was assessed, defined as the closeness of agreement between the measurements obtained using the various devices and a reference standard, in this case, the GOM results. The parameter \"precision\", defined as the reproducibility of digital impression measurements, has been examined in other studies, such as that by [PERSON] et al., where it was evaluated through successive superimposition of scans acquired via IOSs and photogrammetry. The STL files from each group were compared using RMS values [29]. While the findings of this study offer meaningful insights, they are specific to the systems evaluated and should be extrapolated to other devices with caution. Digital impressions were obtained by a single experienced operator to minimize inter-operator variability across the groups [21; 29]. The operator possessed over 7 years of clinical experience in digital dentistry and implant prosthodontics, ensuring competent use of the digital systems involved. Future research incorporating multiple operators could reveal potential differences attributable to variations in clinical expertise. To enhance reproducibility and maintain consistency in data acquisition, the procedures were conducted under standardized environmental conditions, including controlled lighting, temperature, and relative humidity, as advised in the literature [29; 35]. Statistically significant differences of trueness were observed across all implant distributions for each scanning system. For the 3 Shape Trios 3 intraoral scanner, no significant differences were found between the CCI A and CCI B distributions. Similarly, the Medit i500 scanner showed no significant differences between the CCI B and CCI C configurations. Conversely, the photogrammetry device (PIC Dental) demonstrated significant differences only between the CCI A and CCI C distributions. These findings suggest that the trueness provided by the PIC Dental system is less affected by the number and spatial arrangement of dental implants, as CCI A involves six implants, whereas CCI C consists of four implants positioned in closer proximity. A comparative analysis between the reference digital models and the impressions obtained using each method across the various implant distributions revealed that all devices achieved lower RMS values in the CCI C distribution, characterized by fewer implants placed in closer proximity. This observation indicates that for the systems evaluated, a higher number of implants and increased inter-implant distances adversely impact trueness. Additionally, the 3 Shape Trios 3 and Medit i500 intraoral scanners consistently exhibited lower RMS values across all configurations when compared to the PIC Dental system, except for the 3 Shape Trios 3 in the CCI B distribution. This exception suggests that the 3 Shape Trios 3 scanner may be more susceptible to diminished performance with increased inter-implant spacing. Based on the findings of this investigation, the real-time 3D video acquisition technology used in the Medit i500 scanner demonstrated superior performance over long spans compared to the confocal imaging principles employed by the 3 Shape scanner. When evaluating trueness across all scanners, irrespective of implant distribution, the Medit i500 intraoral scanner demonstrated the highest performance, with statistically significant results. It was followed by the 3 Shape Trios 3 intraoral scanner and the PIC Dental photogrammetry system, the latter of which recorded the greatest mean RMS values.