## 3 Results and Discussion
In this study, the ceramic specimens were polished very carefully using a diamond paste and finally 50 nm colloidal silica to avoid any residual stress in the surface layers during polishing [28]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Y-TZP** & **Grain Size (\(\upmu\)m)** & **Phase Fraction (\%)** \\ \hline SM & 0.7 & Tetragonal: 94.9; monoclinic: 2.7 \\ SLA & 0.4 & Tetragonal: 93.6; monoclinic: 3.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Grain size/phase fraction results derived from the EBSD data (Figure 4). Figure 4: EBSD images of the SM- (**a**) and SLA-fabricated (**b**) Y-TZP ceramics (magnification = 5000\(\times\); scale bar = 5 \(\upmu\)m). Figure 3: EDS images of the SM- (**a**) and SLA-fabricated (**b**) Y-TZP ceramics (magnification = 5000\(\times\); scale bar = 5 \(\upmu\)m). BSE, backscattered electron. Flexural strength is an important property used to express indications for the clinical use of ceramics in dental restoration [15]. Table 2 summarizes the flexural strength results of the SM and SLA Y-TZP ceramics, together with their respective Weibull parameters. The Weibull distributions of the flexural strength of the ceramics are presented in Figure 5. For flexural strength, no significant difference was detected between the two ceramics (\(p=0.242\)). In ISO 6872 [20], ceramics are divided into five classes based on their intended clinical use. In addition, for both materials, the mean flexural strength values satisfied the class 5 criteria (>800 MPa) in ISO 6872 [20]. According to class 5 criteria, the recommended clinical indication is monolithic ceramic for the substructure of partial- or full-coverage prostheses of 4 units or more [20]. However, the SM Y-TZP ceramic showed a slightly higher Weibull modulus than did the SLA ceramic, indicating slightly higher reliability and more narrowly distributed flexural strengths of the ceramic fabricated by the conventional method. As shown in Figure 6, the fractured surfaces for both materials showed mixed intergranular and transgranular fractures [29]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Y-TZP**} & \multirow{2}{*}{**Flexural Strength (MPa) 1**} & \multicolumn{3}{c}{**Weibull Parameters 2**} \\ \cline{3-5}  & & \(m\) **(95\% CI)** & \(\sigma_{0}\) **(MPa)** & \(r^{2}\) \\ \hline SM & 927.4 \(\pm\) 134.1 a & 7.7 (6.9–8.5) & 984.6 & 0.97 \\ SLA & 865.7 \(\pm\) 148.5 a & 6.4 (5.8–7.0) & 928.5 & 0.98 \\ \hline \hline \end{tabular}  
* The same lowercase superscript letters show no significant difference between the two different zirconia ceramics (Student’s \(t\)-test, \(p>0.05\)). 2 \(m\), Weibull modulus; CI, confidence interval; \(\sigma_{0}\), Weibull characteristic strength; \(r^{2}\), correlation coefficient.  
\end{table} 
Table 2: Three-point flexural strength values (means \(\pm\) standard deviations) of the SM- and SLA-fabricated Y-TZP ceramics and their respective Weibull parameters. Figure 5: Weibull plots of the three-point flexural strength of the SM- and SLA-fabricated Y-TZP ceramics. The solid lines were obtained from a least-squares fit of the data. Figure 6: SEM images of the fractured surfaces of the SM (**a**) and SLA (**b**) Y-TZP ceramics after the three-point flexural strength test (magnification = 10,000\(\times\); scale bar = 1 \(\upmu\)m). Figure 7 and Table 3 show the fracture toughness data obtained based on the indentation fracture technique. The cracks in the two ceramics revealed a mixed mode involving intergranular and transgranular fractures [30]. The hardness of Y-TZP ceramic tends to decrease with increasing grain size [24]. Similar to the flexural strength results (Table 2), however, there were no significant differences in either the Vickers hardness (\(p\) = 0.480) or fracture toughness (\(p\) = 0.101) between the SM and SLA ceramic materials. This may have been due to only a small difference in grain size between the two materials as well as their similar crystal structures.