## 4 Discussion
Due to their recent emergence, research on chairside additive technology and newly introduced 3D printed hybrid composites is still limited. Initial studies indicate that these materials possess adequate mechanical strength for definitive restorations [15; 37]. However, there is insufficient data on their accuracy, marginal closure precision, and ability to reproduce occlusal and marginal contacts, underscoring the need for further investigation in these areas [38]. The present study investigated and compared the adaptation values of one milled (Tetric CAD) and two 3D printed resin-based crowns using two different techniques (DLP and SLA). The Tetric CAD is a homogenous composite block. SLA-printed Formlabs and DLP-printed Saremco resins were specifically designed for more durable, mid-to-long-term use in the oral cavity. These resin-based materials were selected considering their properties suitable for pediatric crown use. The fit or the misfit is an important factor for clinical success and is often associated with the longevity of the restorations [39]. All measuring techniques have some advantages and drawbacks. [PERSON] et al. [39] compared the 3D triple-scan and the impression replica techniques for three-unit tooth-supported fixed dental prostheses. It was reported that there were no differences in cervical or internal gap values, and both techniques can be used to measure the fit of tooth-supported restorations [39]. The triple-scan protocol is a technique that has become popular due to increasing demands for a digital workflow. In this technique, an optical scanner is employed to capture three types of scans, a scan of the model (prepared tooth), a scan of the inside of the restoration, and a scan of the restoration placed on the model. These scans are then imported into CAD software, where the distances between the model/teeth and the restoration's interior surface (intaglio) can be measured. This information is valuable for ensuring the restoration fits accurately and precisely within the patient's oral cavity [39]. The inner surface of the tooth and the restoration can be seen and measured, and parts or slices can be separated from the data [40]. Progress in digital technologies has made these analyses easier, allowing for comparisons between a product and its CAD file [41]. The triple-scan technique yielded good results but is time-consuming and requires a scanner [22]. In the present study, following the digital workflow, the crowns were designed with an AI design program, subtractively and additively manufactured, and then fit measurements were performed using the triple-scan technique. [PERSON] and [PERSON] [42] compared the marginal and internal fit of machine-milled crowns designed using three CAD software programs (Multi-CAD, Blue-Sky CAD, and InLab). Digital impressions of a prepared molar were used to create crown designs, which were milled and evaluated using the triple-scan protocol and digital analysis. While no significant differences were found in the internal fit of the crowns, InLab-designed crowns demonstrated significantly better marginal fit than Multi-CAD and Blue-Sky CAD. The study concluded that all three CAD programs can produce clinically acceptable crowns but InLab showed superior marginal fit, emphasizing the importance of evaluating CAD software for optimal clinical outcomes. In the present study, a single design was created using the AI dental design program, and all crowns were fabricated based on this same design. The present study observed that production techniques affected the marginal and internal gap values (\(p<0.05\)). The gap values were lower for the DLP-printed group. The milled and DLP-printed groups showed statistically significant differences in marginal and internal gap volumes (\(p<0.05\)). It was observed that DLP-printed resin-based crowns had a better fit. The marginal and internal gap volumes for SLA-printed crowns were between the milled and DLP-printed groups, without showing a significant difference from either group.