## 3 Results  
The results of the marginal adaptation of the investigated groups are shown in Table 1 and Figure 1. The marginal gap for the experimental groups was within the acceptable clinical range (50-100 \(\upmu\)m) (Figure 4). The marginal gap value for premolar and molar abutments varied among the groups in the range of 65.17-84.33 \(\upmu\)m. The Kruskal-Wallis test indicated no significant differences between the groups for each abutment, premolar (\(p=0.76\)) or molar (\(p=0.86\)), in terms of the marginal gap.  
Figure 3: SEM images representing the measurement locations.  
Figure 2: Schematic representation of the measurement points: marginal gap (MG), cervical (C), axial (A), axio-occlusal (AO), occlusal (O).  
The internal gap was evaluated at cervical, axial, axio-occlusal, and occlusal points. The internal fit results of both the monolithic and bi-layered zirconia FDPs are presented in Table 1. The lowest internal gap value was observed at the axial points, whereas the highest gap value was found in the occlusal area in all groups.  
The Kruskal-Wallis test indicated a significant difference between the groups in the axial and axio-occlusal areas (\(p<0.001\)) of both the molar and premolar (Figure 5). In the axial area, the Mann-Whitney U test showed a significant difference in premolar abutment between the ZP and CAD-on groups. At the molar abutment, the Mann-Whitney U test indicated a significant difference between the MZ and ZP groups and between ZP and CAD-on. For the axio-occlusal area, the Mann-Whitney U test showed a significant difference in the molar abutment only between the MZ and ZL, MZ and ZP, ZL and CAD-on, and ZP and CAD-on groups. However, the Kruskal-Wallis test showed no statistically significant difference at the cervical and occlusal measurement points for both premolar and molar abutments.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{**Groups**} & \multicolumn{5}{c}{**Median (\(\mu\)m)**} \\  & & & **(IQR 25 th–75 th)** & & \\ \hline \multirow{5}{*}{**MZ**} & \multirow{2}{*}{Premolar} & Marginal & Cervical & Axial & Axio-Occlusal & Occlusal \\ \cline{3-6}  & & 76.50 & 113.00 & 90.50 & 131.00 & 145.00 \\  & & (50.75–88.25) & (83.50–143.00) & (74.25–112.75) & (81.25–174.00) & (76.50–213.50) \\  & & 76.00 & 116.50 & 80.00 & 87.50 & 150.00 \\  & & (58.25–99.75) & (102.50–136.00) & (58.00–97.50) & (79.75–120.00) & (115.00–230.00) \\ \cline{2-6}  & \multirow{2}{*}{Premolar} & 69.00 & 114.00 & 119.00 & 147.50 & 142.00 \\  & & (63.00–79.25) & (108.50–132.00) & (89.50–125.25) & (95.75–191.75) & (118.50–228.50) \\  & & 81.00 & 129.50 & 106.50 & 175.50 & 161.50 \\  & & (70.00–96.50) & (109.75–14,025) & (82.00–122.00) & (144.50–217.0) & (147.25–267.25) \\ \cline{2-6}  & \multirow{2}{*}{Premolar} & 64.50 & 103.50 & 120.00 & 140.50 & 153.00 \\  & & (54.00–74.50) & (88.00–143.00) & (104.0–130.00) & (122.75–174.0) & (129.25–187.25) \\ \cline{2-6}  & \multirow{2}{*}{Molar} & 77.00 & 127.00 & 119.00 & 186.00 & 167.50 \\  & & (58.00–88.00) & (117.50–135.50) & (117.25–132.0) & (139.00–225.0) & (151.00–240.25) \\ \cline{2-6}  & \multirow{2}{*}{Premolar} & 61.30 & 109.00 & 85.00 & 122.00 & 144.00 \\  & & (47.25–80.00) & (97.50–139.00) & (72.50–93.75) & (95.00–137.00) & (123.50–182.50) \\ \cline{2-6}  & \multirow{2}{*}{Molar} & 75.50 & 118.50 & 86.00 & 128.50 & 163.00 \\ \cline{2-6}  & & (49.00–97.00) & (102.50–144.25) & (81.25–105.00) & (108.25–139.0) & (133.75–249.25) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Marginal and internal gap discrepancy measurements (\(\mu\)m).  
Figure 4: Boxplot representing the marginal gap (\(\mu\)m) measurement of zirconia FDPs.