## 3 Results  
Table 1 represents the results of the reliability tests. The reliability tests showed that, for all the x, y, z measurements of the master model, Groups CI and ISO showed an intraclass correlation coefficient of 1.000, which meant that the data set had almost perfect reliability. The inter-operator reliability also showed an intraclass correlation coefficient of 1.000, which meant that the three measured datasets had a near perfect reliability between three different operators. Table 2 shows a comparison of the absolute trueness between the conventional and digital impressions. An independent two-sample t-test showed that the absolute trueness was significantly different between groups in 35 out of 49 \(\Delta\)x, \(\Delta\)y, Az, and \(\Delta\)D comparisons. Even for the same cylinder position, the trueness favored different impression methods in \(\Delta\)x, \(\Delta\)y, \(\Delta\)z, and \(\Delta\)D comparisons, group CI was more accurate in 26 comparisons while group IOS was more accurate in 9 comparisons, further, the accuracy between the groups was different according to the position of the cylinder. \begin{table}
\begin{tabular}{c c c c} \hline  & & **ICC (95\% CI)** & \(p\) \\ \hline Master model & \(\Delta\)x & 1.000 (1.000–1.000) & \(<\)0.001 \\  & \(\Delta\)y & 1.000 (1.000–1.000) & \(<\)0.001 \\  & \(\Delta\)z & 1.000 (1.000–1.000) & \(<\)0.001 \\ \hline Group CI & \(\Delta\)x & 1.000 (1.000–1.000) & \(<\)0.001 \\  & \(\Delta\)y & 1.000 (1.000–1.000) & \(<\)0.001 \\  & \(\Delta\)z & 1.000 (1.000–1.000) & \(<\)0.001 \\ \hline Group IOS & \(\Delta\)x & 1.000 (1.000–1.000) & \(<\)0.001 \\  & \(\Delta\)y & 1.000 (1.000–1.000) & \(<\)0.001 \\  & \(\Delta\)z & 1.000 (1.000–1.000) & \(<\)0.001 \\ \hline Operators & & 1.000 (1.000–1.000) & \(<\)0.001 \\ \hline \end{tabular}
\end{table} 
Table 1: Reliability test using intraclass correlation coefficient (ICC). \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline  & \multicolumn{3}{c}{Ax} & \multicolumn{3}{c}{**Av**} & \multicolumn{3}{c}{**Av**} & \multicolumn{3}{c}{**Av**} & \multicolumn{3}{c}{**Av**} \\ \hline
**Position** & **Group CI** & **Group IDS** & \(  
Figures 7 and 8 present the amount of \(\Delta\)x, \(\Delta\)y, and \(\Delta\)z at each cylinder position in groups CI and ISO, respectively. In the right quadrant, the amounts of \(\Delta\)x and \(\Delta\)y were inclined negative and greatest at #17C, then values converged on zero as the position of the cylinder got closer to the origin. In the left quadrant, the amounts of \(\Delta\)x and \(\Delta\)y tended to gradually increase as the cylinder positions moved away from the origin. The \(\Delta\)x values were distributed as positive and negative, while the \(\Delta\)y values were mostly negative. The \(\Delta\)z values were relatively small compared to \(\Delta\)x or \(\Delta\)y both in the right and left quadrants. The general tendency of trueness was evaluated using the linear mixed model, and the results showed that the conventional impression method was more accurate than intraoral digital scans for \(\Delta\)x, \(\Delta\)y, \(\Delta\)z, and \(\Delta\)D (\(p\) < 0.05) (Table 3). Table 4 presents the comparison of absolute precision between conventional and digital impressions. The conventional impression method showed a more accurate precision than intraoral digital scans at every  
Figure 8: Distribution of \(\Delta\)x, \(\Delta\)y, and \(\Delta\)z in Group ISO. Vertical axis represents the amount of difference between the master model and digital models (trueness values) in millimeters. Horizontal axis represents the cylinder position according to the axis (i.e., X17 represented \(\Delta\)x at cylinder 17). Figure 7: Distributions of \(\Delta\)x, \(\Delta\)y, and \(\Delta\)z in Group CI. Vertical axis represents the amount of difference between the master model and definitive casts (trueness values) in millimeters. Horizontal axis represents the cylinder position according to the axis (i.e., X17 represents \(\Delta\)x at cylinder 17).