## 4 Discussion
It was hypothesized that smaller FOV settings, due to sharper beam collimation in upper and lower volume areas and an increased contrast-to-noise ratio, could provide greater accuracy. Therefore, models were generated at three different FOV settings. Nevertheless, even at the smallest FOV value of 0.75 mm, marginal and internal fit were still found to be lower than those of the other two models. In relation to this topic, [PERSON] et al. reported a significant difference in cement gap values between 3D model and CBCT groups in their study (\(p<0.001\)). Similar to our findings, the cement gaps of fixed prostheses produced using a 3D laboratory scanner were significantly smaller than those obtained from CBCT data. Similarly, in line with our study, [PERSON] et al. evaluated the marginal fit of CBCT models obtained with three different voxel sizes and extraoral laser scanner models. They found that the marginal gap values of crowns fabricated using the extraoral laser scanner were significantly lower than those of crowns fabricated from CBCT images with 0.3 mm, 0.2 mm, and 0.125 mm voxel sizes--a result that is consistent with our findings (\(p<0.001\)). [PERSON] et al. emphasized in their study that better results were obtained with lower voxel sizes. This situation is similarly supported in our study by the fact that the highest gap values were found in the 0.15 voxel group, which is our highest voxel group. However, as seen in our study, even the model obtained from the lowest voxel group could not reach the success rate of scanner-based models. These results suggest that in the context of fixed prosthetic restorations, CBCT-STL data still require further technological advancements and time to reach the level of accuracy provided by models acquired via laboratory scanners. However, it is important to clarify that the marginal gap values obtained from CBCT-based models in our study (ranging from 464 \(\upmu\)m to 580 \(\upmu\)m) significantly exceed the widely cited clinical threshold of 120 \(\upmu\)m, as reported by [PERSON] and [PERSON]. These values are not clinically acceptable for definitive restorations and highlight the current limitations of CBCT-STL workflows for prosthodonic applications [19; 32; 33; 34]. In a study by [PERSON] et al., similar to our research, the marginal fit of intraoral scanners, model scanners, and CBCT data was evaluated. However, unlike our study, they did not find any statistically significant differences between the groups. Nevertheless, clinically acceptable levels of marginal discrepancy were observed in all three groups [35]. In this study, marginal and internal fit of crown restorations were evaluated by micro-CT method. This non-invasive method is considered as one of the most suitable methods for the evaluation of marginal and internal fit because it allows repeated measurements [36; 37]. Also in our study, to ensure standardization, we directly scanned the prepared tooth using a model scanner. This approach was chosen because involving the conventional model fabrication process would introduce dimensional changes in the dental stone, potentially compromising the standardization of the study. In future studies, the use of conventional impression techniques followed by standardized model fabrication, as suggested, should be considered. As a result of repeated measurements, a statistically significant significance was observed between the coronal and sagittal sections. The lowest cement gap values were obtained with the model scanner, with particularly minimal gap values at the gingival margin. One of the main limitations of the present study is the absence of a true reference (ground-truth) model meant that absolute deviations in fit could not be quantified. As such, our findings are constrained to relative comparisons between scanning methods, which limits the strength of conclusions regarding which modality most closely reproduces the actual tooth geometry.