## 4 Discussion  
The results of this study suggest the rejection of the null hypothesis. Significant differences were found among the marginal and internal gaps of ceramic inlay restorations fabricated through data obtained from CBCT scans, intraoral scanners, and model scanners (\(p<0.05\)). The marginal and internal gaps of inlay restorations fabricated with data obtained from CBCT scans were significantly higher than those of inlay restorations fabricated with data obtained from intraoral and model scanners (\(p<0.05\)). Therefore, the null hypothesis was rejected. Previous studies have indicated that CBCT might be an alternative impression-taking method for implant-supported restorations [3; 20]. Other studies have also reported that data obtained from CBCT can be used for crown restorations [1; 2; 7]. In this study, inlay restoration cavities were scanned by CBCT. The obtained DICOM data were converted to STL format, and the inlay restorations were designed and fabricated. Studies have reported that marginal and internal fit are very important for prosthetic restorations. Poor marginal and internal fit can lead to issues such as secondary caries, microleakage, and reduced fracture resistance [4; 11; 12; 21; 22]. Moreover, restorations with excessive gaps may compromise long-term durability and necessitate additional clinical adjustments, such as chairside corrections or remakes, thereby increasing treatment time and cost. In this study, the inlay restorations fabricated with CBCT data exhibited significantly greater marginal and internal gap dimensions compared to those produced with intraoral and model scanners. Although some studies have indicated that a clinically acceptable marginal gap for CAD-CAM restorations is between 58 and 200 \(\upmu\)m [17], most studies have emphasized that the marginal gap should be below 120 \(\upmu\)m [4; 12; 15; 23]. Accordingly, in the present study, 120 \(\upmu\)m was adopted as the primary reference value to assess clinical acceptability. The marginal gap values of ceramic inlay restorations fabricated with intraoral and model scanner data were measured to be an average of 97.00 \(\pm\) 10.12 \(\upmu\)m for intraoral scanners and 109.67 \(\pm\) 9.72 \(\upmu\)m for model scanners. For inlays fabricated with data obtained from CBCT, the average marginal gap value was 169.27 \(\pm\) 38.64 \(\upmu\)m. The marginal gap values for intraoral and model scanners are below the clinically acceptable value of 120 \(\upmu\)m. However, for the CBCT group, the average values are above the clinically acceptable limit of 120 \(\upmu\)m. It should be noted, though, that these values are still below \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Marginal Fit**} & \multicolumn{2}{c}{**Internal Fit**} \\ \hline \multirow{2}{*}{**Group**} & \multirow{2}{*}{**N**} & \multicolumn{2}{c}{**Mean \(\pm\) SD**} & \multicolumn{2}{c}{**Mean \(\pm\) SD**} & \multirow{2}{*}{**Mean \(\pm\) SD**} & \multirow{2}{*}{**95\% CIM (\(\upmu\)m)**} & \multirow{2}{*}{**95\% CIM (\(\upmu\)m)**} \\  & & \multicolumn{2}{c}{**LB**} & & & & \\ \hline CBCT & 11 & 169.27 \(\pm\) 38.64 \({}^{\text{a}}\) & 143.31 & 195.24 & 224.64 \(\pm\) 49.98 \({}^{\text{a}}\) & 191.06 & 258.22 \\ Intraoral Scanner & 11 & 97.00 \(\pm\) 10.12 \({}^{\text{b}}\) & 90.20 & 103.80 & 124.55 \(\pm\) 26.51 \({}^{\text{b}}\) & 106.73 & 142.36 \\ Model Scanner & 11 & 109.67 \(\pm\) 9.72 \({}^{\text{b}}\) & 102.15 & 117.18 & 153.73 \(\pm\) 19.02 \({}^{\text{b}}\) & 140.94 & 166.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Descriptive statistics of marginal fit and internal fit. the 200 um threshold mentioned in some studies. Nevertheless, gap values exceeding 120 um may compromise the seal and structural integrity of the restoration under functional loading, potentially reducing clinical longevity [17].