## 3 Results  
The trueness was influenced by the presence of an HA (\(F\) = 48.155, \(p\) < 0.05), the scanner (\(F\) = 104.722, \(p\) < 0.05), and the location of missing teeth (\(F\) = 14.600, \(p\) < 0.05). There was no significant interaction between these factors. The results of pairwise comparisons among factors are shown in Figure 4. The trueness in each group is summarized in Table 1. The results indicate that there were significant differences between almost all of the HA  
Figure 3: Linear measurements made using the “linear dimension” function after resegmenting a scan. Values are in millimeters. groups (HA-2, HA-3, and HA-4) and NHA groups (NHA-2, NHA-3, and NHA-4), with the exceptions of HA-3 and NHA-3 for the Trios 3 IOS. Additionally, there were significant differences between all three IOSs, with the trueness being best for the Trios 3 IOS, followed by the CS3600 and i500 IOSs. The pairwise comparisons based on the number of missing teeth revealed a significant difference only between groups with two teeth missing and groups with four teeth missing. The precision was influenced by the presence of an HA (\(F\) = 34.291, \(p\) \(<\) 0.05), the scanner (\(F\) = 312.483, \(p\)\(<\) 0.05), the location of missing teeth (\(F\) = 35.107, \(p\)\(<\) 0.05), and the interaction between the location of missing teeth and the scanner (\(F\) = 10.535, \(p\)\(<\) 0.05). The results of pairwise comparisons among factors are shown in Figure 5. The precision in each group is summarized in Table 2. The results indicate that the precision was significantly higher in groups with an HA. Additionally, there were significant differences between all of the scanners, with the precision being best for the T500 scanner, followed by the Trios 3, CS3600, and i500 IOSs. The pairwise comparisons based on the number of missing teeth revealed significant differences between groups with two teeth missing and groups with three teeth missing, as well as between groups with two teeth missing and groups with four teeth missing. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**IOS** & **HA-2** & **HA-3** & **HA-4** & **NHA-2** & **NHA-3** & **NHA-4** \\ \hline Trios 3 & 36.0 \(\pm\) 5.4 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}}\) & 41.8 \(\pm\) 11.5 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}}\) & 49.8 \(\pm\) 10.0 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}}\) & 46.0 \(\pm\) 5.1 \({}^{\rm\,\,\beta\rm{\rm{\AA}}}\) & 47.7 \(\pm\) 2.8 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}c}\) & 63.9 \(\pm\) 17.2 \({}^{\rm\,\,\beta\rm{\rm{\AA}}d}\) \\ CS3600 & 49.1 \(\pm\) 12.7 \({}^{\rm\,\,\alpha\rm{\AA}a}\) & 62.3 \(\pm\) 5.3 \({}^{\rm\,\,\alpha\rm{\rm{\rm{\AA}}b}}\) & 66.8 \(\pm\) 10.4 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}b}\) & 60.9 \(\pm\) 11.6 \({}^{\rm\,\,\beta\rm{\rm{\AA}}}\) & 68.1 \(\pm\) 9.1 \({}^{\rm\,\,\beta\rm{\rm{\rm{\AA}}a}}\) & 79.0 \(\pm\) 11.8 \({}^{\rm\,\,\beta\rm{\rm{\rm{\AA}}a}}\) \\ i500 & 69.3 \(\pm\) 27.0 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}}\) & 77.2 \(\pm\) 9.7 \({}^{\rm\,\,\alpha\rm{\rm{\AA}}a}\) & 92.6 \(\pm\) 13.1 \({}^{\rm\,\,\alpha\rm{\rm{\rm{\AA}}b}}\) & 94.4 \(\pm\) 15.2 \({}^{\rm\,\,\beta\rm{\rm{\rm{\AA}}a}}\) & 101.5 \(\pm\) 20.4 \({}^{\rm\,\,\beta\rm{\rm{\rm{\AA}}a}}\) & 112.8 \(\pm\) 21.4 \({}^{\rm\,\,\beta\rm{\rm{\rm{\AA}}a}}\) \\ \hline \end{tabular} Different Greek letters indicate significant differences between the HA and NHA groups. Different uppercase letters indicate significant differences between IOSs. Different lowercase letters indicate significant differences between groups with different locations of missing teeth (HA-2 vs. HA-3 vs. HA-4, NHA-2 vs. NHA-3 vs. NHA-4) (\(p\)\(<\) 0.05).  
\end{table} 
Table 1: Trueness values in the HA-2, HA-3, HA-4, NHA- 2, NHA-3, and NHA-4 groups for the three intraoral scanners (IOSs). Eight scans were performed in each group. Data are mean \(\pm\) standard deviation values in micrometers.