## 2 Materials and Methods  
The ceramic crown preparation was performed on typodont maxillary first premolar. Tooth preparation was made by an experienced prosthodontist (B.A.) for complete-coverage zirconia incorporating 2 mm occlusal reduction, 1 mm axial reduction, and 360\({}^{\circ}\) 1 mm deep chamfer margin with rounded internal line angles. The restoration was fabricated with milling single-feldspathic ceramic blocks (CEREC Blocks; Sirona Dental Systems GmbH, Bensheim, Germany).  
The crown preparation was scanned with an intraoral scanner (CEREC Omnicam system, Sirona Dental Systems GmbH, Bensheim, Germany), a model scanner (in EOS X5, Sirona Dental Systems GmbH, Bensheim, Germany), and CBCT (Planmeca Promax 3D Max Machine, Helsinki, Finland).  
CBCT scans were performed with 3 different voxel sizes (0.075 mm, 0.1 mm, and 0.15 mm), the smallest distinguishable box-shaped unit of a three-dimensional digital image. These voxel sizes were chosen to reflect commonly used clinical resolutions in dental CBCT imaging, balancing diagnostic detail and radiation exposure, as supported by prior studies [24, 25]. To standardize the imaging technique, all scans were acquired at 90 kVp, 12 mA, and a field of view (FOV) size of 50 \(\times\) 40 mm. The DICOM data obtained from CBCT scans (Planmeca Promax 3D Max) were converted into STL format using the Planmeca Romexis software (version 6.2, Helsinki, Finland), which includes automated segmentation and mesh generation capabilities. To reduce voxel-induced surface noise and artifacts, the software's built-in surface processing functions were used, including smoothing and contour optimization algorithms. All conversions were performed using consistent segmentation thresholds and under identical lighting and model orientation conditions. While these filtering steps aim to enhance surface continuity and suppress digital noise, the potential influence of voxel resolution and segmentation limitations on the final geometry must be acknowledged. No manual editing was applied to the mesh data to preserve comparability across groups. These steps were taken to ensure that STL models accurately reflect the reconstructed geometries derived from each CBCT voxel size and remain suitable for downstream CAD design and fit analysis.  
Crown restorations for the upper first premolar were designed by transferring the 3D STL images obtained from the intraoral scanner, laboratory scanner, and CBCT scans to a CAD software (Cerec CAD System Sirona Dental Systems GmbH, Bensheim, Germany). The cement gap was set as 120 \(\upmu\)m in the marginal area and 200 \(\upmu\)m in the remaining areas inside the crown restoration. After the design of the total crown restoration was completed, the crown restorations were milled using feldspathic blocks (CEREC Blocks; Sirona Dental Systems GmbH, Bensheim, Germany) on a milling machine (Cerec In Lab MC XL, Sirona Dental Systems).  
In this study, marginal fit was defined as the perpendicular distance between the crown margin and the preparation finish line. Internal fit refers to the space between the inner surface of the crown and the axial or occlusal surfaces of the tooth. The cement gap is the designed internal spacing within the CAD software intended to accommodate the luting agent, which was set at 120 \(\upmu\)m near the margins and 200 \(\upmu\)m internally. These definitions were used consistently throughout the study.  
Marginal gap and internal fit values were measured using MCT. The high-resolution scanning capable Skyscan 1275 (Skycan, Kontich, Belgium) was used for MCT scans. Scanning parameters were set as follows: 125 kVp, 80 mA, 20 \(\upmu\)m/pixel, and a rotation step of 0.2. A 1 mm thick aluminum filter was used to prevent artifacts during the scans. Subsequently, each scanned sample was reconstructed individually using Skyscan's NRecon (version 1.7.4.6 Skyscan, Kontich, Belgium) software.