## 4 Discussion
selected for the current study due to the following considerations: (i) it quantifies overall deviations across the entire dataset; (ii) it enables straightforward comparisons between different scanning technologies; and (iii) by incorporating all data points, RMS values reduce potential biases associated with specific reference points or planes, making the method less operator-dependent than linear or angular measurement techniques [34]. It is worth noting that the accuracy of an impression method is defined by two primary parameters: trueness and precision. According to the International Organization for Standardization (ISO), \"accuracy\" is 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, while \"precision\" (repeatability) refers to the closeness of agreement between different impression results, obtained under similar conditions [35; 36; 37; 38; 39]. Although insightful, the results of the present study are specific to the systems evaluated and should be applied with caution to other devices. In this study, digital impressions were taken by a single operator experienced in the abovementioned techniques to minimize variability among groups [39]. The operator was proficient in the digital technologies employed, with more than 5 years of clinical experience in digital dentistry and implant prosthodontics. Future studies involving multiple operators may help identify potential variations among professionals with different levels of experience. To enhance reproducibility and ensure reliable data acquisition, controlled room conditions of light, temperature, and relative humidity were implemented in this study, as recommended in the literature [40]. Concerning precision assessment by implant distribution per device, statistically significant differences were found in RMS values among the groups scanned with the IOs of 3 Shape Trios 3 and Medit i500 scanners. However, no differences were observed among the groups evaluated with the PIC Dental photogrammetry scanner, suggesting that the precision provided by this device is not influenced either by the number or the position of dental implants. All scanners studied demonstrated high precision levels across all implant distributions. A detailed analysis revealed that the 3 Shape Trios 3 and Medit i500 IOs exhibited very low RMS values in the CCI C distribution, whereas for the CCI A distribution, a similar performance was obtained among all scanners. Additionally, the PIC Dental scanner produced slightly lower RMS values than the IOs in the CCI B implant distribution. The highest mean RMS values were observed in the Tr4_B group (16.96 \(\upmu\)m), but these still reflect high precision. Photogrammetry-based scanning was the only approach in which no statistically significant differences were found across multiple pairwise comparisons (Pi6_A, Pi4_B, and Pi4_C). Notably, the discrepancies identified in our work are smaller than those reported by studies evaluating the best passive adjustment [14; 32]. When assessing the precision of all scanners regardless of implant distribution, high performance was also observed, with the Medit i500 IOs showing the best precision (although without statistical significance), followed by the IO 3 Shape Trios 3 scanner, and the PIC Dental photogrammetry device. In fact, no statistically significant differences were found when considering only the digital scanner systems, indicating high repeatability among the devices evaluated. As previously mentioned, a full comparison of these results with the available literature is hindered by the use of diverse scanning devices and variable experimental conditions. Although without statistical significance, the PIC-based photogrammetry yielded the highest mean RMS values. This pattern aligns with the findings of [PERSON] et al., who, in contrast to our data, reported statistical differences among the technologies assessed.