# A Comparison of Dental Arch Width and Length on 3D Digital and Plaster Models
## 3 Results
### Comparison of Methods for Measuring Maximally ICW  
The statistically significant differences were observed between the methods with a large effect size (\(p\) \(<\) 0.001; \(\eta^{2}\) = 0.427; Table 3). The manual measurements significantly differed from all digital methods in the range from 0.72 mm to 0.83 mm. In contrast, no significant differences were observed between the digital methods within the range from 0.03 mm to 0.12 mm. The agreement between the three methods was excellent (ICC = 0.904; 95% CI 0.780-0.956; \(p\) \(<\) 0.001), with a small measurement error (ME = 0.47).  
When comparing the difference between manual measurements and the digital measurements made on intraoral scans, the agreement was good (ICC = 0.844; 95% CI 0.459-0.941; \(p\) \(<\) 0.001; Table 4). The measurement error was small (ME = 0.62 mm), and a statistically significant fixed deviation of 0.72 mm was detected compared to the hypothetical mean deviation of 0 mm (\(p\) \(<\) 0.001). The confidence interval was relatively wide, ranging from \(-\)1.00 to 2.43, with 93.3% of the subjects' measurements falling within this range (only two cases were outside the range). A strong correlation (r = 0.899; \(p\) \(<\) 0.001) was found between manual measurements and digital measurements obtained from the intraoral scan.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Intaoral Scan (IOS)**} & \multicolumn{3}{c}{**Digitalized Plaster Model Obtained**} & \multicolumn{3}{c}{**Digitalized Plaster Model Obtained**} & \multicolumn{3}{c}{**Paster Model (PM)**} \\  & & & & & & & & & & & & \\  & & & & & & & & & & & & \\ \hline Mar1 & 0.16 \(\pm\) 0.27 & 0.255 & 0.05 & 0.30 \(\pm\) 0.57 & 0.142 & 0.10 & 0.27 \(\pm\) 0.24 & 0.065 & 0.08 & 0.02 \(\pm\) 0.04 & 0.374 & 0.01 \\ M1 CW & 0.01 \(\pm\) 0.01 & 0.907 & 0.0 & 0.01 \(\pm\) 0.28 & 0.178 & 0.07 & 0.01 \(\pm\) 0.07 & 0.01 & 0.00 & 0.02 \(\pm\) 0.04 & 0.374 & 0.01 \\ M1 MW & \(-\)0.55 \(\pm\) 0.30 & 0.014 & 0.17 & \(-\)0.07 \(\pm\) 0.28 & 0.591 & 0.02 & 0.08 \(\pm\) 0.07 & 0.073 & 0.03 & \(-\)0.04 \(\pm\) 0.09 & 0.374 & 0.01 \\ M1 MW & 0.04 \(\pm\) 0.48 & 0.874 & 0.01 & 0.07 \(\pm\) 0.45 & 0.754 & 0.02 & 0.00 \(\pm\) 0.08 & 0.958 & 0.00 & 0.06 \(\pm\) 0.09 & 0.208 & 0.02 \\ M2V & 0.08 \(\pm\) 0.76 & 0.821 & 0.03 & 0.00 \(\pm\) 0.95 & 0.996 & 0.00 & 0.16 \(\pm\) 0.22 & 0.165 & 0.05 & \(-\)0.18 \(\pm\) 0.06 & 0.54 & 0.06 \\ M4 AP & 0.12 \(\pm\) 0.53 & 0.637 & 0.04 & 0.07 \(\pm\) 0.80 & 0.846 & 0.02 & 0.03 \(\pm\) 0.17 & 0.683 & 0.01 & 0.08 \(\pm\) 0.23 & 0.477 & 0.03 \\ \hline \end{tabular}
\end{table}
Table 2: Random and systematic errors of measurements on different models between two examiners.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Parameter** & **IOS** & **DPMA Mean \({}^{*}\)\(\pm\) SD** & **DPMS Mean \({}^{*}\)\(\pm\) SD** & **PM**  
Comparing the difference between manual measurements and the digital measurements obtained from digitized models made from the alginate impression, a good agreement was observed (ICC = 0.821; \(p\)! 0.001; Table 4), with a small measurement error of 0.63 mm. A statistically significant fixed deviation of 0.83 mm was detected compared to the hypothetical mean deviation of 0 mm (\(p\)! 0.001). The confidence interval was relatively  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  
wide, ranging from \(-0.90\) to \(2.57\), with 93.3% of the subjects' measurements falling within this range (only two cases were outside the range).  
Similarly, when comparing manual measurements with the digital measurements obtained from digitized models made from the silicone impression, a good agreement was observed, with a small measurement error (ICC = 0.831; \(p<0.001\), ME = 0.60 mm; Table 4). Additionally, a statistically significant fixed deviation of 0.80 mm was detected. The measurements from 96.7% of subjects were within the confidence interval.