## 3 Results  
The summaries of the results are shown in Tables 1 and 2. The average crown retrieval times for lithium disilicate were 267.1 \(\pm\) 130.43, 220 \(\pm\) 79.09, 277.1 \(\pm\) 126.44 s for LD1, LD2, and LD3, respectively. On the other hand, the ones for zirconia were 368.4 \(\pm\) 136.14, 355 \(\pm\) 159.39, and 419.2 \(\pm\) 121.36 s for Z1, Z2, and Z3, respectively. There was a statistical difference overall (ANOVA, \(p\) = 0.009); however, there was no statistical difference within the same material (ANOVA, \(p\) = 0.5 for lithium disilicate, and \(p\) = 0.56 for zirconia). When comparing the restorative materials, zirconia crown retrieval takes approximately 100-200 s longer than lithium disilicate one with statistical significance except for the first retrieval experiment (\(t\)-test, \(p\) = 0.11, \(p\) = 0.03 and \(p\) = 0.02 for first, second, and third retrieval, respectively). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample Grouping \#** & **LD1** & **LD2** & **LD3** & **Z1** & **Z2** & **Z3** \\ \hline
1 & 172 & 153 & 172 & 192 & 286 & 361 \\
2 & 243 & 223 & 243 & 443 & 315 & 255 \\
3 & 235 & 175 & 235 & 335 & 167 & 428 \\
4 & 188 & 204 & 188 & 214 & 325 & 331 \\
5 & 470 & 234 & 470 & 506 & 466 & 429 \\
6 & 180 & 230 & 180 & 374 & 465 & 236 \\
7 & 400 & 422 & 400 & 545 & 566 & 550 \\
8 & 176 & 183 & 276 & 300 & 183 & 551 \\
9 & 132 & 138 & 132 & 230 & 182 & 483 \\
10 & 475 & 238 & 475 & 545 & 595 & 568 \\ Average & 267.1 & 220 & 277.1 & 368.4 & 355 & 419.2 \\ Standard deviation & 130.43 & 79.09 & 126.44 & 136.14 & 159.39 & 121.36 \\ ANOVA & & & LD1, LD2, LD3, Z1, Z2, and Z3 & & & \\ All group & & & \(p\) = 0.009 \({}^{*}\) & & & & \\ ANOVA & & & LD1, LD2 and LD3 & & & & \\ Within material & & & \(p\) = 0.50 & & & & \\ \(t\)-test & & LD1 and Z1 & LD2 and Z2 & & LD3 and Z3 & \\  & & & & \(p\) = 0.11 & \(p\) = 0.03 \({}^{*}\) & & \(p\) = 0.02 \({}^{*}\) \\ \hline \hline \end{tabular} \({}^{*}\) level of significance \(\alpha\) = 0.05; \({}^{\bullet}\) LD: lithium disilicate; Z: zirconia; 1, 2, and 3: First, second, and third retrieval trials.  
\end{table} 
Table 1: Er:YAG laser-assisted crown retrieval time (sec). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample Grouping \#** & **LD1** & **LD2** & **LD3** & **Z1** & **Z2** & **Z3** \\ \hline
1 & 25 & 22.7 & 24.9 & 21 & 21.1 & 19.6 \\
2 & 23.7 & 23.7 & 26.8 & 21.4 & 24.2 & 22 \\
3 & 26.5 & 28.6 & 25 & 22.8 & 25 & 21.2 \\
4 & 27.3 & 23.6 & 23.2 & 20.5 & 27.8 & 21.7 \\
5 & 22.8 & 24.9 & 23.4 & 22.5 & 23.8 & 22 \\
6 & 24.1 & 25 & 24.1 & 23.2 & 22.7 & 22 \\
7 & 22.4 & 23.5 & 22.1 & 24.6 & 23.5 & 22.6 \\
8 & 22.1 & 28.2 & 25.3 & 24 & 23.9 & 21.5 \\
9 & 24.1 & 24.9 & 25 & 24.6 & 25 & 22.4 \\
10 & 21.5 & 23.5 & 21.9 & 24.2 & 23.3 & 24.9 \\
**Average** & 23.95 & 24.86 & 24.17 & 22.88 & 24.03 & 21.99 \\
**Standard deviation** & 1.89 & 2.01 & 1.53 & 1.51 & 1.74 & 1.32 \\ ANOVA & & & LD1, LD2, LD3, Z1, Z2, and Z3 & & \\ All group & & & \(p\) = 0.006 \({}^{*}\) & & & \\ ANOVA & & LD1, LD2 and LD3 & & & & \\
**Within material** & & & \(p\) = 0.52 & & & \\ \(t\)**-test** & & & & & & \\ \hline \hline \end{tabular} \({}^{*}\) level of significance \(\alpha\) = 0.05; \({}^{\bullet}\) LD: lithium disilicate; Z: zirconia; 1, 2, and 3: First, second, and third retrieval trials.  
\end{table} 
Table 2: Maximal temperatures (\({}^{\circ}\)C) during Er:YAG laser irradiation. The maximum temperatures for lithium disilicate were \(23.95.1\pm 1.89\)\({}^{\circ}\)C, \(24.86\pm 2.01\)\({}^{\circ}\)C, and \(24.17\pm 1.53\)\({}^{\circ}\)C for LD1, LD2, and LD3, respectively. The maximum temperatures for zirconia were \(22.88\pm 1.51\)\({}^{\circ}\)C, \(24.03\pm 1.74\)\({}^{\circ}\)C, and \(21.99\pm 1.32\)\({}^{\circ}\)C for Z1, Z2, and Z3. There was a statistical difference overall (ANOVA, \(p=0.006\)) and within the zirconia group (ANOVA, \(p=0.02\)), while no statistical difference was noted within the lithium disilicate group (ANOVA, \(p=0.52\)).