# Impact of Dental Model Height on Thermoformed PET-G Aligner Thickness--An In Vitro Micro-CT Study
## 3 Results
### Comparison of Thickness Values at Measurement Locations  
Linear mixed effects models revealed a significant effect of group and measurement location (\(p<0.001\), respectively), as well as for their interaction (\(p<0.001\)). Thickness values were slightly higher in N group at most of the locations. With respect to the measurement location, thickness values were smallest at facial surfaces and highest at incisal faces. Thickness values were also higher at cusp tips compared to the fissures (occlusion surface), and within a medium range at palatal surfaces (Figure 5). Post-hoc multiple comparison revealed significant differences at facial and palatal surfaces (Table 4). Within-group comparison revealed significant differences between all measurement locations except palatal and palatal-cervical, respectively (Table 5). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Comparison**} & **Est. (SE) Group** & **Est. (SE) Group** & **Est. Difference** & \\  & **H** & **N** & **(SE)** & \(p\)**-Value** \\ \hline Cusp tip & 0.372 (0.003) & 0.384 (0.003) & \(-0.012\) (0.004) & 0.090 \\ Occlusal & 0.285 (0.003) & 0.278 (0.003) & 0.007 (0.004) & 0.902 \\ Incisal & 0.427 (0.003) & 0.434 (0.003) & \(-0.008\) (0.004) & 0.751 \\ Facial & 0.243 (0.003) & 0.268 (0.003) & \(-0.025\) (0.004) & \(<\)0.001 *** \\ Facial-cervical & 0.222 (0.003) & 0.224 (0.003) & \(-0.002\) (0.004) & 1.000 \\ Palatal & 0.332 (0.003) & 0.347 (0.003) & \(-0.015\) (0.004) & 0.005 ** \\ Palatal-cervical & 0.327 (0.003) & 0.339 (0.003) & \(-0.012\) (0.004) & 0.073 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Between-group comparison of local thickness values (mm) from group high (H) and narrow (N) aggregated for measurement location. Comparison was achieved using a multiple comparison post hoc test with Tukey-method for \(p\)-value adjustment (family of 14 estimates), respectively. *** \(p<0.01\), *** \(p<0.001\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Estimate (SE)** & **Estimate (SE)** & **Est. Difference** & \\  & **Group H** & **Group N** & **(SE)** & \(p\)**-Value** \\ \hline Molar & 0.316 (0.002) & 0.324 (0.002) & \(-0.003\) (0.003) & 0.077 ** \\ Premalor & 0.309 (0.002) & 0.320 (0.002) & \(-0.011\) (0.003) & 0.007 ** \\ Canine & 0.315 (0.002) & 0.330 (0.002) & \(-0.015\) (0.003) & \(<\)0.001 *** \\ Front & 0.311 (0.002) & 0.323 (0.002) & \(-0.012\) (0.003) & 0.002 ** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Estimated mean [standard error (SE)] for the local thickness values (mm) from group high (H) and narrow (N) aggregated by tooth type. Comparison was achieved using multiple comparison post hoc test with Tukey-method for \(p\)-value adjustment (family of 8 estimates). ** \(p<0.01\), *** \(p<0.001\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Comparison** & \multicolumn{2}{c}{**Estimated Difference (SE)**} & **T-Ratio** & \(p\)**-Value** \\ \hline \multirow{4}{*}{Group H} & canine–front & 0.003 (0.003) & 1.903 & 0.251 \\  & canine–molar & \(-0.001\) (0.003) & \(-0.571\) & 0.940 \\  & canine–premolar & 0.006 (0.003) & 3.545 & 0.008 ** \\  & front–molar & \(-0.004\) (0.002) & \(-2.561\) & 0.074 \\  & front–premolar & 0.003 (0.002) & 1.700 & 0.344 \\  & molar–premolar & 0.007 (0.002) & 4.261 & 0.001 ** \\ \hline \multirow{4}{*}{Group N} & canine–front & 0.007 (0.003) & 2.770 & 0.044 * \\  & canine–molar & 0.006 (0.003) & 2.493 & 0.081 \\ \cline{1-1}  & canine–premolar & 0.011 (0.003) & 4.323 & \(<\)0.001 ** \\ \cline{1-1}  & front–molar & \(-0.001\) (0.003) & \(-0.277\) & 0.992 \\ \cline{1-1}  & front–premolar & 0.004 (0.003) & 1.553 & 0.420 \\ \cline{1-1}  & molar–premolar & 0.006 (0.003) & 1.830 & 0.279 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Within-group comparison of local thickness values (mm) for group high (H) and narrow (N) aggregated for tooth type. Comparison was achieved using multiple comparison post hoc test with Tukey-method for \(p\)-value adjustment (family of 4 estimates), respectively. * \(p<0.05\), ** \(p<0.01\), *** \(p<0.001\).