## 3 Results  
### Color Change (\(\Delta\)E)  
Material type, surface finishing, and their interactions had a significant impact on the \(\Delta\)E (\(p<0.05\)) (Table 3).  
Figure 3: Schematic presentation of three-ball piston setup for BFS test.  
The mean \(\Delta\)E values of the surface-finished materials are presented in Table 4. Among the materials, CS and VE demonstrated the highest (2.40 \(\pm\) 0.38) and lowest (1.39 \(\pm\) 0.46) \(\Delta\)E values. Regarding the surface finishing, OG specimens were more color stable (1.67 \(\pm\) 0.44), and control specimens were least color stable (2.39 \(\pm\) 0.49).  
Post hoc [PERSON]'s test was used to determine the pairs with a significant difference in \(\Delta\)E. Most surface finishing protocols showed insignificant differences (\(p\) > 0.05), except for the control and the surface-finished LU materials (\(p\) < 0.01) and between control and OG or MP+PP of CS (\(p\) < 0.01) (Table 5).  
Post hoc multiple comparisons for \(\Delta\)E of the materials after surface finishing.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Group** & **LU** & **VE** & **CS** & **CU** & **Overall** \\ \hline Control & 2.98 \(\pm\) 0.36 & 1.75 \(\pm\) 0.73 & 2.79 \(\pm\) 0.23 & 2.06 \(\pm\) 0.61 & 2.39 \(\pm\) 0.49 \\ \hline MP & 2.05 \(\pm\) 0.36 & 1.37 \(\pm\) 0.46 & 2.49 \(\pm\) 0.34 & 1.92 \(\pm\) 0.48 & 1.96 \(\pm\) 0.43 \\ \hline OG & 1.75 \(\pm\) 0.38 & 1.21 \(\pm\) 0.33 & 2.03 \(\pm\) 0.51 & 1.69 \(\pm\) 0.53 & 1.67 \(\pm\) 0.44 \\ \hline MP+PP & 2.00 \(\pm\) 0.34 & 1.22 \(\pm\) 0.32 & 2.29 \(\pm\) 0.42 & 1.88 \(\pm\) 0.31 & 1.85 \(\pm\) 0.35 \\ \hline Overall & 2.19 \(\pm\) 0.38 & 1.39 \(\pm\) 0.46 & 2.40 \(\pm\) 0.38 & 1.89 \(\pm\) 0.48 & 1.97 \(\pm\) 0.43 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mean \(\Delta\)E of the materials after surface finishing protocols.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variation Recourses** & **Sum of Squares** & **df** & **Mean Square** & **F** & **Sig** \\ \hline Materials & 27.66 & 3 & 9.22 & 45.92 & 0.000 \({}^{*}\) \\ \hline surface finishing & 13.68 & 3 & 4.56 & 22.71 & 0.000 \({}^{*}\) \\ \hline Materials \(\times\) surface finishing & 3.61 & 9 & 0.40 & 2.00 & 0.042 \({}^{*}\) \\ \hline \hline \end{tabular} \({}^{*}\)Statistically significant (\(p\) < 0.05).  
\end{table}
Table 3: MANOVA of \(\Delta\)E.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Materials**} & \multirow{2}{*}{**Surface Finishing**} & \multicolumn{4}{c}{**Dunnett’s Multiple Comparison**} \\ \cline{3-6}  & & **Control** & **MP** & **OG** & **MP+PP** \\ \hline \multirow{4}{*}{LU} & Control & 1 & & & \\ \cline{2-6}  & MP & 0.000 \({}^{*}\) & 1 & & \\ \cline{2-6}  & OG & 0.000 \({}^{*}\) & 0.427 & 1 & \\ \cline{2-6}  & MP+PP & 0.000 \({}^{*}\) & 1.000 & 0.440 & 1 \\ \hline \multirow{4}{*}{VE} & Control & 1 & & & \\ \cline{2-6}  & MP & 0.597 & 1 & & \\ \cline{2-6}  & OG & 0.187 & 0.909 & 1 & \\ \cline{2-6}  & MP+PP & 0.197 & 0.926 & 1.000 & 1 \\ \hline \multirow{4}{*}{CS} & Control & 1 & & & \\ \cline{2-6}  & MP & 0.115 & 1 & & \\ \cline{2-6}  & OG & 0.002 \({}^{*}\) & 0.106 & 1 & \\ \cline{2-6}  & MP+PP & 0.012 \({}^{*}\) & 0.749 & 0.699 & 1 \\ \hline \multirow{4}{*}{CU} & Control & 1 & & & \\ \cline{2-6}  & MP & 0.987 & 1 & & \\ \cline{2-6}  & OG & 0.554 & 0.856 & 1 & \\ \cline{1-1} \cline{2-6}  & MP+PP & 0.923 & 1.000 & 0.883 & 1 \\ \hline \hline \end{tabular} \({}^{*}\)Statistically significant (\(p\) < 0.05).  
\end{table}
Table 5: Post hoc multiple comparisons for \(\Delta\)E of the materials after surface finishing.