## 1 Introduction  
In recent years, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies have gained wide adoption for dental procedures. CAM in dentistry includes subtractive manufacturing (SM: milling) or additive manufacturing (AM) technologies. Subtractive manufacturing, commonly called milling technology, has been used in dentistry for many years. Milling the restorations from prefabricated homogenous blocks or disks minimizes possible manipulation errors. Furthermore, the quality and geometry of the marginal area are greatly affected by the shape and size of the milling tools and the number of axes on the milling machines used to fabricate them [1, 2, 3, 4]. In recent years, additive manufacturing (3D printing) systems have been integrated into clinical practice because of their possible advantages, such as the ability to produce complex restorations and cost-efficient fabrication with less material waste [5]. Instead of SM, AM has introduced several advantages to the production field, including mass production, minimal material waste, the creation of complex geometries, minimal residual stresses, and the elimination of tool wear [6; 7; 8]. However, additive manufacturing also has drawbacks, including dimensional inaccuracies, lengthy printing times, inconsistent post-processing steps among various printing methods, layer shrinkage, dimensional changes due to printing parameters, and variations in the physical and surface properties of the final product [6; 9; 10]. Of several available AM technologies, digital light processing (DLP) and stereolithography (SLA) have been commonly used methods for dental procedures due to their high accuracy and resolution [5; 11; 12]. Digital light processing (DLP) and stereolithography (SLA) are similar 3D printing technologies; however, DLP uses a digital projector to flash an entire image of the layer across the build platform, while SLA employs a laser to selectively solidify points within a photosensitive resin layer. DLP printers, which use materials sensitive to visible light, generally achieve faster print times than SLA printers [12; 13]. SM and AM technologies have widely been used in adult crown restoration clinical settings. In pediatric dentistry, using advanced techniques such as subtractive and additive manufacturing is still relatively new and has also contributed to the excitement for esthetic solutions [14; 15]. Crown adaptation is crucial in pediatric dentistry, significantly impacting the success and durability of restorations in primary teeth. Well-fitted crowns help to minimize issues like microleakage, secondary caries, and periodontal complications. Since children may not maintain optimal oral hygiene, proper crown adaptation helps to protect the restored tooth by preventing bacterial infiltration and minimizing wear on adjacent teeth. Furthermore, achieving a precise fit is important for ensuring comfort and functionality, especially in young patients, as poorly adapted crowns can cause discomfort, impair chewing, and lead to early failure. Considering the distinct anatomy and smaller dimensions of primary teeth, ensuring the proper adaptation of pediatric crowns is key to achieving both functional and esthetic results while also safeguarding the health of surrounding oral tissues [16; 17; 18]. There is no reported ideal method for measuring marginal and internal gaps, while various methods are used to measure the fit of restorations. Although digital systems have been used to produce well-fitted restorations, factors such as the production method, material type, cement spacing settings, and milling system can all influence the fit of crowns [19; 20]. Considering the limited lifespan of primary teeth, which remain in the oral cavity only until the natural exfoliation phase, it is desirable for crowns on primary teeth to last until the shedding period without needing replacements. Using permanent resin materials rather than interim resins offers a practical and potentially superior option for pediatric restorations.