## 4 Discussion  
There are many studies in the literature evaluating the marginal and internal fit of prosthetic dental restorations using different methods such as scanners, CBCT, and STL models [16; 17; 18; 19; 26; 27]. In this study, three different methods of digital model acquisition were evaluated: intraoral scanning, model scanning, and CBCT-based STL reconstruction using three different FOVs. The aim was to compare the marginal and internal fit of the prosthetic restorations generated from each method. Quantitative analyses revealed that the model scanners had the lowest marginal gap of 77 \(\pm\) 36 \(\upmu\)m and the lowest internal gap of 117 \(\pm\) 58 \(\upmu\)m. These values emphasize that the model scanners are the most suitable models in terms of marginal and internal fit. All tomography-based models showed lower internal and marginal fit compared to scanner-based models, but the highest gap value was found in the model obtained with 0.15 voxel size tomography with 580 \(\pm\) 204 \(\upmu\)m and 502 \(\pm\) 106 \(\upmu\)m at the marginal and internal, respectively. This situation was attributed to the loss of resolution as the voxel size increases. Specifically, the external marginal fit of restorations derived from intraoral and model scanning was found to be superior to that of CBCT-derived models. The scanner-based datasets demonstrated more ideal cement space dimensions, particularly in the marginal regions. This finding is clinically significant, as adequate marginal fit is a key determinant of long-term success in fixed prosthodontics. Marginal gaps exceeding 120 \(\upmu\)m have been consistently associated with increased risk of periodontal disease and secondary caries formation. When cement spaces surpass this critical threshold, they require a greater volume of luting agent, which can result in higher plaque accumulation, marginal microleakage, and the development of microcracks within the restorative material. Such biologic and mechanical complications have been identified as primary contributors to early prosthetic failure. Therefore, ensuring optimal marginal fit particularly through high-resolution scanning techniques plays a crucial role in improving the prognosis and longevity of fixed dental restorations [19; 28; 29; 30]. In a study conducted by [PERSON] et al., a maxillary first molar tooth was used to create three different digital models: a control model obtained by scanning the extracted tooth with a 3D laboratory scanner; a virtual 3D model generated directly from CBCT data (CBCTscan group); and another virtual model (CBCT-CAD group) produced by designing a polyurethane model using CBCT data and CAD software, which was then rescanned. The vertical marginal discrepancy (VMD) values of monolithic zirconia crowns fabricated on these models were measured under a microscope. The mean VMD was reported as 41 \(\upmu\)m in the control group, 44 \(\upmu\)m in the CBCTscan group, and 60 \(\upmu\)m in the CBCT-CAD group. No statistically significant difference was found between the control and CBCTscan groups (\(p\) = 0.274). However, there was a statistically significant difference between the CBCT-CAD group and both the control and CBCTscan groups (\(p\) < 0.001). These findings indicated that the 3D laboratory scanner group demonstrated superior marginal fit compared to the other groups. This result is in line with the findings of our study. However, in contrast to our methodology, only the laboratory scanner was evaluated in the mentioned study, and intraoral scanners were not utilized. Additionally, unlike our study, a prosthetic crown restoration model was not obtained directly from the CBCT data; instead, a digital model was created by rescanning a physical model derived from the CBCT dataset [31]. In our study, the crowns obtained using both intraoral and model scanners demonstrated statistically significantly better fit.