## 3 Results
The RMSE was lowest for the ISB with its flat surface facing the buccal direction and full scanning (buccal-full:47.02 \(\pm\) 5.91 \(\upmu\)m), and highest for the ISB with its flat surface facing the proximal direction and partial scanning (proximal-partial: 74.91 \(\pm\) 3.99 \(\upmu\)m). The CS3600 scanner also showed significant differences in one-way analysis (\(F\) = 25.929, \(p\) < 0.001), with the RMSE being lowest for buccal-full (56.09 \(\pm\) 7.74 \(\upmu\)m) and proximal-full (69.79 \(\pm\) 11.18 \(\upmu\)m), and highest for proximal-partial (102.79 \(\pm\) 9.22 \(\upmu\)m). The i500 scanner also showed a significant difference in one-way analysis (\(F\) = 22.046, \(p\) < 0.001), with the RMSE being lowest for buccal-full (60.91 \(\pm\) 10.74 \(\upmu\)m). The common result for all scanners was that in the case of prealignment data, the RMSE was the lowest for buccal-full and the highest for proximal-partial. Postalignment data on trueness according to combinations of the ISB orientation and scanning method for each scanner are shown in Figure 6. For the T500 scanner, the RMSE was lower in the buccal groups (14.34 \(\pm\) 0.89 \(\upmu\)m) than in the proximal groups (29.35 \(\pm\) 1.15 \(\upmu\)m, \(p\) < 0.001). The TRIOS 3 scanner showed significant differences in one-way analysis according to the ISB orientation and scanning method (\(F\) = 5.342, \(p\) < 0.005), with the RMSE being lower for buccal-full (19.45 \(\pm\) 8.42 \(\upmu\)m) than for buccal-partial (31.89 \(\pm\) 6.07 \(\upmu\)m) and proximal-partial (31.20 \(\pm\) 6.70 \(\upmu\)m). For the CS3600 scanner, the RMSE values did not differ between the groups (\(F\) = 0.059, \(p\) = 0.981). The i500 scanner showed significant differences in one-way analysis (\(F\) = 3.369, \(p\) = 0.032), with the RMSE  
Figure 4: Overall trueness in the postalignment 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. being lower for buccal-full (26.18 \(\pm\) 10.11 \(\upmu\)m) and buccal-partial (32.69 \(\pm\) 7.31 \(\upmu\)m) than for proximal-partial (36.54 \(\pm\) 3.08 \(\upmu\)m). Figures 7 and 8 show representative images from the trueness evaluation of test data for the i500 scanner. Figure 7 shows prealignment data for the deviation of the ISB areas, which was higher in the proximal groups (Figure 7C,D) than in the buccal groups (Figure 7A,B), and higher in the partial-scan groups (Figure 7B,D) than in the full-scan groups (Figure 7A,C). Figure 8 shows postalignment data for the deviation of the abutment areas, which was higher in the proximal groups (Figure 8C,D) than in the buccal groups (Figure 8A,B), and higher in the partial-scan groups (Figure 8B,D) than in the full-scan groups (Figure 8A,C). Comparing the prealignment and postalignment images reveals that the degree of deviation tended to be lower in the postalignment data. Figure 5: Trueness in the prealignment data for each scanner according to combinations of the ISB orientation and scanning method: (**A**) T500, (**B**) TRIOS 3, (**C**) CS3600, and (**D**) i500. Data are mean and SD values. Different letters indicate significant differences. Figure 6: Trueness in the postalignment data for each scanner according to combinations of the ISB orientation and scanning method: (**A**) T500, (**B**) TRIOS 3, (**C**) CS3600, and (**D**) i500. Data are mean and SD values. Different letters indicate significant differences.