## 4 Discussion
The higher gap values observed in the milled group were thought to be related to the milling tools used. SLA-printed and DLP-printed crowns were produced using different light source technologies, and the permanent crown resins used in both systems were also different. [PERSON] et al. [43] found that additively manufactured (AM) crowns exhibited significantly superior marginal and internal fits compared to subtractively manufactured (SM) crowns. However, [PERSON] et al. [44] investigated the overall internal fit of interim crowns created by AM and SM techniques and found no statistically significant difference. [PERSON] et al. [5] investigated the trueness of the crowns fabricated by using additively (Crowntec) and subtractively (Brilliant Crios, breCAM.monoCOM, and G-CAM) manufactured resin-based CAD-CAM materials. It was stated that the material type affected the trueness of the resin-based crowns. The clinical fit of the materials tested may be comparable, as the differences from the virtual design file at the occlusal, intaglio occlusal, and marginal surfaces were minimal. However, the tested 3D printed composite resin crowns showed similar or greater deviations on the overall and external surfaces than milled crowns. [PERSON] et al. [36] investigated the marginal and internal fit of crowns manufactured by additive (NextDent C&B) and subtractive manufacturing (Vita Enamic) techniques. The marginal and internal fit of the crowns were assessed both before and after cementation, using the replica technique and by sectioning the crown and tooth. The marginal fit of additively manufactured crowns was similar to those made with the chairside subtractive technique and fell within clinically acceptable limits. However, neither technique consistently outperformed the other in terms of internal fit. Although the replica technique is widely used and validated for assessing crowns' marginal and internal fit, it has some limitations. One drawback is the limited number of measurement points, which may not fully capture the circumferential fit of the crown. However, its extensive use in prosthodontics facilitates comparison with other studies [10; 45]. [PERSON] et al. [46] reported that the layer thickness and build orientation affected the marginal fit and internal gap volume of the 3D printed fixed partial dentures. The 3D internal gap volume of the 3D printed prosthesis was smaller than the subtractively manufactured prosthesis. [PERSON] et al. [47] reported that 3D cement space volumes were 12.6 \(\pm\) 1.6 and 15.1 \(\pm\) 2.8 for milled resin matrix crowns. Although these results are similar to our study, a direct comparison cannot be made due to the difference in measurement methods between the two studies. This study has some limitations. Only one type of material was tested for each manufacturing technique, and material variations might influence the results. The accuracy of the milling unit and the milling tools, 3D printing techniques, and 3D printing parameters may influence the fit of crowns. Further research is needed to evaluate how different milling and 3D printing technologies and settings impact dental restorations' overall accuracy and clinical performance. All crowns in the study were cemented using firm finger pressure, a method commonly employed in routine dental practice due to its practicality and ease of use. However, this technique introduces a potential source of variability, as the applied seating pressure may differ from clinician to clinician and cannot be consistently replicated across cases. The lack of a standardized or controlled pressure may result in inconsistent crown seating, leading to variations in marginal fit, cement layer thickness,and, ultimately, the overall performance of the restorations. These inconsistencies could affect the mechanical properties, such as fracture resistance and the longevity of the crowns.