## 4 Discussion  
The first null hypothesis (H\({}_{0}\)1), which states that there are no differences in precision based on the scanner used, was accepted, as no statistically significant differences were observed among the various scanners assessed. The second null hypothesis (H\({}_{0}\)2), which posits that there are no differences in precision according to the various implant distributions (CCI A, option with six implants, two implants in the position of the lateral incisors, two anterior to the mental foramen, and two in the region of the first molars; CCI B, option with four implants, two implants in the canine position and two implants in the first molar region; and CCI C, option with four implants, two implants in the position of the lateral incisors and two implants anterior to the mental foramen), was rejected, as the results indicated that the CCI C distribution, characterized by the lowest number of implants and their closer proximity to one another, yielded significantly more favorable results. On the other hand, the CCI B distribution was the one that presented the worst results. Full-arch implant-supported restorations present a challenge for achieving reliable intraoral scanning. Inaccuracies may arise from limited anatomical landmarks, the extensive presence of mobile mucosa, the uniform morphology and increased spacing between implant sandwicies, or the summation of intrinsic errors in the image acquisition process due to an expanded scanning area [30]. This in vitro study analyzed and compared the precision of various digital impression methods in full-arch implant rehabilitation. Two IOs and a photogrammetry-based scanner were assessed. The former two (the 3 Shape Trios 3 using confocal technology and the Mediti 1500, based on the principle of 3D video technology in motion) capture data within a small area, while the latter determines the spatial positions of implants, including distances and angulations, based on calibrated marker coordinates (PIC Dental) [22; 28; 31; 32]. These IOs were chosen because (i) they represent distinct scanning principles, whereas PIC Dental scanner employs a photogrammetry-based approach, enabling a comprehensive comparison of precision across different scanning methodologies, and (ii) they are commonly used in clinical practice, making the findings more applicable to real-world scenarios. The Carames Classification for implant distribution was followed because it provides a standardized system for implant positioning in the jawbone and is widely accepted in the field of implant dentistry [27]. The data analysis was conducted using the best-fit alignment methodology by calculating the root mean square (RMS) value, with successive superimpositions performed to assess precision [29]. Alternative approaches have been described in the literature to assess the accuracy of IOs, including linear and angular measurements without superimpositions, mean 3D deviations, absolute distance measurements, and deviations along the X, Y, and Z axes after applying a best-fit algorithm [33]. The RMS method does not convey comprehensive information about the nature or distribution of errors, and it is algorithm-dependent [22]. This dependency can introduce variability based on the method used and may fail to capture localized deviations. Despite these limitations, the RMS method was \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Device** & **RMS \(\pm\) 95\% CI (\(\mu\)m)** & **Min; Max (\(\mu\)m)** & \(n\) & \(p\) \\ \hline IO 3 Shape Trios 3 & 11.86 [10.42; 13.30] & 3.80; 45.60 & 135 & \\ \hline IO Mediti 1500 & 11.80 [10.90; 12.70] & 2.80; 37.10 & 135 & 0.097 \\ \hline Photogrammetry & 12.42 [11.33; 13.50] & 1.90; 27.20 & 135 & \\ PIC Dental & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Descriptive statistics and comparison of precision test parameters among different devices (\(\mu\)m).