## 3 Results  
The overall mean marginal gap values and standard deviations (SDs) for the experimental groups are displayed in Table 1. The paired-sample \(t\)-test results indicate a significant increase in the marginal gap values of the PEKK group after five years of simulated aging (\(p\) < 0.001). No significant difference was observed in the titanium group (\(p\) = 0.071). After thermocycling, it was found that the PEKK group showed a significantly higher mean marginal gap value (84.99 \(\pm\) 44.28 \(\upmu\)m) than before (81.75 \(\pm\) 44.53 \(\upmu\)m). In the titanium group, however, no significant difference was found when comparing before (44.04 \(\pm\) 24.16 \(\upmu\)m) and after (44.65 \(\pm\) 24.15 \(\upmu\)m) thermocycling. There was no significant influence of cyclic loading on the vertical marginal gap in either experimental group (Table 1). The means and SDs of the change in marginal gap values for the tested groups after each aging condition are shown in Table 2. Significant differences were observed in post-thermal cycling and post-simulated aging among the groups. The Student's \(t\)-test results indicate that the PEKK group had a significantly higher marginal gap change than the titanium group after thermocycling (\(p\) = 0.003) and five-year simulated aging (\(p\) = 0.002). When differences in marginal gap change values between measuring points (Figure 3) were analyzed within each group, the Friedman test results revealed no statistically significant differences (Table 3). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Group (n)**} & \multicolumn{6}{c}{**Mean Marginal Gap (SD)**} \\ \cline{2-9}  & \multirow{2}{*}{**Initial**} & \multicolumn{2}{c}{**After**} & \multirow{2}{*}{**\(p\)-Value**} & \multicolumn{2}{c}{**After Cyclic**} & \multirow{2}{*}{**\(p\)-Value**} & \multicolumn{2}{c}{**After Five-Year**} & \multirow{2}{*}{**\(p\)-Value**} \\  & & **Therocycling** & & & & & **Aging** \\ \hline Titanium (12) & 44.04 (24.16) & 44.65 (24.15) & 0.209 & 44.72 (24.11) & 1.00 & 44.72 & 28.61/60.83 & 0.071 \\ Percentile: 25/75 & 30.12/59.32 & 29.15/58.24 & 28.61/60.83 & 28.61/60.83 & 28.61/60.83 & 28.61/60.83 & 0.001 \\ \hline PEKK (12) & 81.75 (44.53) & 84.99 (44.28) & 85.31 (44.43) & 85.31 (44.43) & 85.31 (44.43) & 85.31 (39.31/123.85) & 85.31 (39.31/123.85) & 0.000 1 \\ Percentile: 25/75 & 36.36/120.50 & 39.11/121.65 & 39.11/121.65 & 39.31/123.85 & 39.31/123.85 & 0.000 1 \\ \hline \hline \end{tabular}  
* indicates statistically significant difference (\(p\)-value < 0.05).  
\end{table} 
Table 1: Mean (\(\upmu\)m) values of vertical marginal gap of three-unit FPDs initially, after different aging conditions and a five-year simulation. The fracture load results are presented in Table 4. A statistically significant difference was observed between the two groups (\(p<0.001\)), where the titanium group exhibited superior mechanical strength with a fracture load higher than that of the PEKK group (3050 \(\pm\) 385.30 and 1359.14 \(\pm\) 205.49 N, respectively). Figure 5 provides a graph of mean load (N) vs. extension (mm) for both experimental groups. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Ultimate Fracture Load (N)**} & \multicolumn{1}{c}{\(p\)**-Value**} \\ \cline{2-4}  & **Titanium** & **PEKK** & \\ \hline Mean & 3050.18 & 1359.14 & _0.000 a_ \\ (SD) & (385.30) & (205.49) & _0.000 a_ \\ \hline \hline \end{tabular}  
* indicates statistically significant. (\(p\)-value \(<\) 0.05).  
\end{table} 
Table 4: Fracture load (N) of three-unit FPDs fabricated with different materials after five-year simulated aging. Figure 5: Load-extension graphs of experimentally veneered FPDs fabricated with PEKK and titanium group.