## 3 Results  
### Vickers Hardness  
The reliability of the Vickers hardness test ranged from moderate (ICC = 0.58) to excellent (ICC = 0.99). The mean Vickers hardness (in HV0.5) and standard deviations ranged from 13.50 \(\pm\) 2.62 to 29.16 \(\pm\) 6.83 for the untreated subgroups. After the specimens were autoclaved with cycle 1, the Vickers hardness ranged from 6.94 \(\pm\) 2.21 to 27.67 \(\pm\) 5.42. After being subjected to cycle 2, the Vickers hardness ranged from 10.52 \(\pm\) 1.05 to 25.30 \(\pm\) 1.65. The results of the Vickers hardness test are given in Table 2, and corresponding boxplots are provided in Figure 3. In three out of five resin/printer groups, the Kruskal-Wallis test pointed at qualitative differences (group 0, group 2, and group 3). In these groups, a post hoc test was conducted. In group 0, the Vickers hardness of the specimens autoclaved with cycle 1 significantly decreased and almost halved compared to the untreated control (\(p<0.001\)), whereas cycle 2 yielded significantly higher Vickers hardness values (\(p<0.001\). In group 2, the Vickers hardness of cycle 1 increased slightly (\(p=0.359\)) compared to the untreated control, whereas the Vickers hardness of the cycle 2 subgroup was significantly lower compared to the untreated control and cycle 1 groups (\(p<0.001\), respectively). In group 3, a higher Vickers hardness was found for both autoclaving protocols (untreated vs. cycle 1: \(p=0.010\); untreated vs. cycle 2: \(p<0.001\)), whereas no significant differences were found between the two autoclaving cycles. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & & \multicolumn{2}{c}{**Vickers**} & & & & \multicolumn{2}{c}{**Bonferroni-Corrected Post Hoc Test**} & & \\  & & & **Hardness** & & & & & **(Mann–Whitney-U, If Pt Pt \textless{} 0.05)** & & & \\
**Group \$ & **ICC** & **Subgroup \$ & **M \(\pm\) SD** & **H (2)** & **P**H & **Comparison** & **U** & **z** & **p**U & **r** \\ \hline \multirow{4}{*}{0} & \multirow{4}{*}{0.993} & untreated & 13.50 \(\pm\) 2.62 & \multirow{4}{*}{35.896} & \multirow{4}{*}{\(<\)0.001 ***} & untreated & \multirow{4}{*}{8} & \multirow{4}{*}{\(-\)4.334} & \multirow{4}{*}{\(<\)0.001 ***} & \multirow{4}{*}{\(-\)0.791} \\  & & cycle 1 & 6.94 \(\pm\) 2.21 & & & & & & \\  & & cycle 2 & 19.57 \(\pm\) 2.04 & & & & & & \\  & & & & & & & & & \\ \hline \multirow{4}{*}{1} & \multirow{4}{*}{0.582} & untreated & 29.16 \(\pm\) 6.83 & \multirow{4}{*}{5.847} & \multirow{4}{*}{0.054} & - & - & - & - & - \\  & & cycle 1 & 27.67 \(\pm\) 5.42 & & & & & & & \\  & & cycle 2 & 25.30 \(\pm\) 1.65 & & & & & & \\ \hline \multirow{4}{*}{2} & \multirow{4}{*}{0.945} & untreated & 14.14 \(\pm\) 2.33 & \multirow{4}{*}{26.303} & untreated & \multirow{4}{*}{75} & \multirow{4}{*}{\(-\)1.555} & \multirow{4}{*}{0.359} & \multirow{4}{*}{\(-\)0.284} \\  & & & & & & & & & \\  & & cycle 1 & 16.00 \(\pm\) 3.06 & & & & & & \\  & & cycle 2 & 10.52 \(\pm\) 1.05 & & & & & & \\  & & & cycle 2 & & & & & & \\ \hline \multirow{4}{*}{3} & \multirow{4}{*}{0.925} & untreated & 17.12 \(\pm\) 1.96 & \multirow{4}{*}{22.659} & untreated & \multirow{4}{*}{42} & \multirow{4}{*}{\(-\)2.924} & \multirow{4}{*}{\(0.010\) *} & \multirow{4}{*}{\(-\)0.534} \\  & & cycle 1 & 20.80 \(\pm\) 2.95 & & & & & & \\  & & cycle 2 & 23.84 \(\pm\) 2.24 & & & & & & \\  & & cycle 2 & & & & & & \\  & & & cycle 2 & & & & & \\ \hline \multirow{4}{*}{4} & \multirow{4}{*}{0.670} & untreated & 15.67 \(\pm\) 2.41 & \multirow{4}{*}{0.398} & - & - & - & - & - \\  & & cycle 1 & 16.96 \(\pm\) 2.92 & 1.844 & 0.398 & - & - & - & - \\ \cline{1-1}  & & cycle 2 & 14.74 \(\pm\) 1.25 & & & & & & \\ \hline \hline \end{tabular}  
* \(p<0.05\); ** \(p<0.01\); **\(p<0.001\); **\(p<0.001\); **\(p=9\) specimens for each of the 5 groups; **\(p=3\) specimens for each of the 15 subgroups; Pt Pt \(p\)-value from Kruskal–Wallis test; Pt \(p\)-value from Mann–Whitney-U test.  
\end{table} 
Table 2: Results of the Vickers hardness test and statistical analysis. Figure 3: Boxplots: Vickers hardness of the different groups and subgroups.