## 1 Introduction  
The use of computer-aided design and manufacturing (CAD-CAM) systems has become increasingly common in prosthetic dentistry. The process of capturing digital impressions and generating three-dimensional virtual models is routinely applied to various prosthetic materials provided as prefabricated blocks [1]. A digital model can be obtained using either intraoral scanners or model scanners [2, 3]. Intraoral scanners are fully digital systems that offer numerous advantages, allowing for precise scans. However, due to their high cost, they may not always be accessible in clinics, and their use can sometimes be challenging within the oral cavity. Model scanners are another well-known method of obtaining digital models, but they involve the inconvenient step of creating a stone model from a traditional impression. The traditional impression process can induce a gag reflex in patients, the sterilization of the impression material is difficult, distortion of the impression may occur, and there are many complex steps involved in the traditional impression process, all of which make the use of model scanners challenging [1; 2; 3; 4; 5]. Additionally, a significant limitation of both optical scanning methods is the loss of detail in areas where light cannot reach, such as between adjacent teeth and undercut areas [6]. CBCT, which provides essential 3D diagnostic information to dentists, has recently started to be used for prosthetic applications, in addition to procedures like producing surgical stents for implant placement. It is also considered an alternative method to intraoral and model scanners. Studies have indicated that although data scanned with CBCT are not as accurate as those obtained with intraoral and model scanners, they still provide clinically acceptable levels of accuracy [1; 2; 4; 7]. CBCT data are in the Digital Imaging and Communications in Medicine (DICOM) format and therefore need to be converted to Standard Triangulation Language (STL) format to be used with other digital systems such as CAD/CAM systems, which operate in STL format. To overcome this issue, software that converts DICOM data to STL data is used. This allows DICOM data converted to STL format to be used in CAD/CAM systems, which is particularly useful in prosthetic dentistry. The accuracy of STL data obtained from CBCT depends on the quality of the DICOM data and the conversion software [8]. The ability to reproduce an accurate impression of the prepared teeth and the surrounding tissues is pivotal in the prosthetic workflow [9]. The impression transfers the intraoral situation, and the accuracy of this transfer influences the marginal and internal fit of the restorations, an important factor in the longevity of the final restoration [10]. Poor marginal fit can lead to microleakage, secondary caries, dissolution of the luting cement, and gingival inflammation [4; 11]. Additionally, inadequate internal fit may lead to increased cement thickness, influence occlusion, compromise retention, weaken the fracture resistance of restorations, and consequently contribute to poor marginal fit. Marginal and internal adaptation play a critical role in inlay restorations, since their margins are subjected to physical, mechanical, and thermal loads [11; 12; 13]. Marginal fit is generally defined as a straight-line contact or a gap-less transition between the preparation and the margin of the restoration. Several studies have shown different values for clinically acceptable marginal fit; nonetheless, a universally accepted standard has yet to be established [14]. In addition to studies indicating that gaps smaller than 120 \(\upmu\)m are clinically acceptable [15], there are studies suggesting that an ideal margin gap is between 50 and 100 \(\upmu\)m [16]. Furthermore, there are studies indicating that the marginal gap for CAD-CAM restorations should be in the range of 58-200 \(\upmu\)m [17].