## 3 Results  
The ICC for upper C3 was 0.978, demonstrating good repeatability.  
Tables 2 and 3 show descriptive analysis and the results of the paired \(t\)-test for both upper and lower arches.  
In the upper arch, no statistically significant differences between measurements emerged. The only exception was the difference at Z6-Z6, the distance between the thickest areas of the gingiva, which was significant (\(p\) = 0.002). The \(\Delta\) (difference between means) between C.stl and AL.stl was 0.39 mm (Figure 3).  
In the lower arch, a statistically significant difference also emerged between for Z6-(\(p\) = 0.014) and for MVC6 (\(p\) = 0.019), the latter being the distance between the mesio-buccal cusp tips on the upper first molars. The \(\Delta\) was 0.26 mm and 0.4 mm for Z6 and MVC6, respectively (Figures 4 and 5).  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & \multicolumn{3}{c}{**C.stl**} & \multicolumn{6}{c}{**AL.stl**} \\ \hline  & **Mean \(\pm\) SD** & **Median** & \
\begin{tabular}{c} **25 th–75 th** \\ **Percentile** \\ \end{tabular} & **Mean \(\pm\) SD** & **Median** &
\begin{tabular}{c} **25 th–75 th** \\ **Percentile** \\ \end{tabular} & **\(\Delta\)** & \(p\)**-Value** \\ \hline ZC3 & 25.09 \(\pm\) 2.11 & 25.23 & 23.73–25.74 & 25.30 \(\pm\) 2.18 & 24.99 & 24.07–26.10 & 0.21 & 0.064 \\ \hline C3 & 34.60 \(\pm\) 2.05 & 34.70 & 33.61–35.70 & 34.32 \(\pm\) 1.91 & 34.39 & 32.90–35.67 & 0.28 & 0.310 \\ \hline CG4 & 36.12 \(\pm\) 1.92 & 35.88 & 35.10–37.55 & 36.04 \(\pm\) 1.89 & 36.10 & 34.81–37.70 & 0.08 & 0.557 \\ \hline VC4 & 41.97 \(\pm\) 2.34 & 42.28 & 40.83–44.01 & 41.64 \(\pm\) 2.12 & 42.02 & 40.20–42.91 & 0.3 & 0.076 \\ \hline Z6 & 34.81 \(\pm\) 2.71 & 34.22 & 32.61–37.68 & 34.42 \(\pm\) 2.62 & 34.05 & 32.39–36.76 & 0.39 & 0.002 * \\ \hline MVC6 & 50.93 \(\pm\) 3.20 & 50.51 & 49.05–53.34 & 50.88 \(\pm\) 3.09 & 50.72 & 49.37–53.51 & 0.05 & 0.312 \\ \hline DPC6 & 41.31 \(\pm\) 3.12 & 40.58 & 39.03–44.41 & 41.09 \(\pm\) 3.18 & 40.49 & 38.81–44.10 & 0.22 & 0.258 \\ \hline \end{tabular}
\end{table}
Table 2: Descriptive statistics and paired \(t\)-test for upper arch measurements. SD: standard deviation; \(\Delta\): difference between means. Statistical significance\({}^{\text{st}}\): \(p\) < 0.05.  
Figure 2: Example of measurement on AL.stl file on Ortho Viewer Software (3 Shape, Copenhagen, Denmark).  
Figure 4: Scatter plot of lower Z6 measurements. X axis: C.stl data; Y axis: AIAstl data.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**C.stl**} & \multicolumn{4}{c}{**AIAstl**} \\ \hline  & **Mean \(\pm\) SD** & **Median** & \multicolumn{2}{c}{**25 th–75 th**} & \multicolumn{2}{c}{**Mean \(\pm\) SD**} & **Median** & \multicolumn{2}{c}{**25 th–75 th**} & \multicolumn{1}{c}{**\(\Delta\)**} & \multicolumn{1}{c}{\(p\)-Value**} \\ \hline ZC3 & 20.02 \(\pm\) 1.45 & 20.15 & 18.73–21.39 & 20.21 \(\pm\) 1.64 & 20.72 & 18.57–21.51 & 0.19 & 0.195 \\ \hline C3 & 26.49 \(\pm\) 1.87 & 26.71 & 25.50–27.84 & 26.40 \(\pm\) 1.77 & 26.76 & 25.55–27.66 & 0.09 & 0.398 \\ \hline CG4 & 30.49 \(\pm\) 1.87 & 30.78 & 29.38–31.63 & 30.33 \(\pm\) 1.78 & 30.70 & 29.07–31.43 & 0.16 & 0.106 \\ \hline VC4 & 34.48 \(\pm\) 1.92 & 34.74 & 33.21–35.54 & 34.44 \(\pm\) 1.85 & 34.72 & 32.71–36.02 & 0.04 & 0.728 \\ \hline Z6 & 33.99 \(\pm\) 2.73 & 34.22 & 32.40–35.39 & 33.73 \(\pm\) 2.77 & 33.94 & 32.43–35.15 & 0.26 & 0.014 * \\ \hline MVC6 & 45.56 \(\pm\) 2.92 & 45.93 & 44.38–47.71 & 45.16 \(\pm\) 2.75 & 45.40 & 44.43–47.00 & 0.4 & 0.019 * \\ \hline DPC6 & 38.13 \(\pm\) 3.00 & 38.21 & 35.97–40.24 & 37.88 \(\pm\) 2.97 & 38.31 & 35.85–39.98 & 0.25 & 0.056 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Descriptive statistics and paired \(t\)-test for lower arch. SD: standard deviation; \(\Delta\): difference between means. Statistical significance *: \(p\) < 0.05.  
Figure 3: Scatter plot of upper Z6 measurements. X axis: C.stl data; Y axis: AIAstl data.