## 3 Results  
The precision of the reference scan was 7.23 \(\pm\) 0.34 \(\upmu\)m (mean \(\pm\) SD) when the flat surface of the ISB faced the buccal direction, and 6.84 \(\pm\) 0.34 \(\upmu\)m when it faced the proximal direction. One of these data was randomly selected as the reference data for the trueness evaluation of the test data. Prealignment data on trueness according to the ISB orientation, scanning method, and type of intraoral scanner are shown in Figure 3. The three-way ANOVA of prealignment data revealed that all main effects of ISB orientation (\(F\) = 65.493, \(p\) < 0.001), scanning method (\(F\) = 137.794, \(p\) < 0.001), and scanner type were statistically significant (\(F\) = 47.865, \(p\) < 0.001). Analysis of two-way interactions revealed significant interaction effects of the scanning method and the scanner type (\(F\) = 8.177, \(p\) = 0.001), while the other interaction effects were not statistically significant (ISB orientation and scanning method: \(F\) = 3.343, \(p\) = 0.071; ISB orientation and scanner type: \(F\) = 0.015, \(p\) = 0.985). The three-way interaction effect of the ISB orientation, scanning method, and scanner type was not statistically significant (\(F\) = 2.445, \(p\) = 0.093). The overall RMSE according to the ISB orientation and scanning methods was lower in the buccal groups (67.50 \(\pm\) 18.56 \(\upmu\)m) than in the proximal groups (82.80 \(\pm\) 16.73 \(\upmu\)m), and lower in the full-scan groups (64.05 \(\pm\) 14.74 \(\upmu\)m) than in the partial-scan groups (86.24 \(\pm\) 16.59 \(\upmu\)m). RMSE values for the overall prealignment data according to the type of intraoral scanner were significantly lower for the TRIOS 3 device (62.46 \(\pm\) 11.51 \(\upmu\)m) than for the CS3600 (78.73 \(\pm\) 20.76 \(\upmu\)m, \(p\) < 0.001) and i500 (84.25 \(\pm\) 17.30 \(\upmu\)m, \(p\) < 0.001) devices. Postalignment data on trueness according to the ISB orientation, scanning method, or type of intraoral scanner are shown in Figure 4. The three-way ANOVA of postalignment  
Figure 3: Overall trueness in the prealignment data according to (**A**) ISB orientation, (**B**) scanning method, and (**C**) type of intraoral scanner. Data are mean and SD values. Different letters indicate significant differences. data revealed that there were significant main effects of the ISB orientation (\(F\) = 4.811, \(p\) = 0.031) and scanning method (\(F\) = 6.022, \(p\) = 0.016), but not of the scanner type (\(F\) = 3.104, \(p\) = 0.050). Analysis of two-way interactions revealed that there were no significant interaction effects of the ISB orientation and scanning method (\(F\) = 2.446 \(p\) = 0.122), ISB orientation and scanner type (\(F\) = 1.061, \(p\) = 0.351), or scanning method and scanner type (\(F\) = 1.241, \(p\) = 0.294). The three-way interaction effect of the ISB orientation, scanning method, and scanner type was not statistically significant (\(F\) = 0.454, \(p\) = 0.636). The overall RMSE according to the ISB orientation and scanning methods was significantly lower in the buccal groups (28.15 \(\pm\) 8.87 \(\upmu\)m) than in the proximal groups (31.94 \(\pm\) 8.95 \(\upmu\)m), and significantly lower in the full-scan groups (27.92 \(\pm\) 10.80 \(\upmu\)m) than in the partial-scan groups (32.16 \(\pm\) 6.35 \(\upmu\)m). RMSE values for the overall postalignment data according to the type of intraoral scanner were significantly lower for the TRIOS 3 device (27.61 \(\pm\) 8.33 \(\upmu\)m) than for the i500 device (32.84 \(\pm\) 8.13 \(\upmu\)m, \(p\) = 0.040). Prealignment data on trueness according to combinations of the ISB orientation and scanning method for each scanner are shown in Figure 5. For the T500 scanner, the RMSE was significantly lower in the buccal groups (33.45 \(\pm\) 1.50 \(\upmu\)m) than in the proximal groups (56.91 \(\pm\) 3.60 \(\upmu\)m, \(F\) = 4.088, \(p\) < 0.001). The TRIOS 3 scanner showed significant differences in one-way analysis according to ISB orientation (\(F\) = 32.923, \(p\) < 0.001).