# Accuracy of 3D-Printed Master Cast Workflow Using a Digital Light Processing Primer  
[PERSON]  
1 Department of Prosthodontics and Biomaterials, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany; [EMAIL_ADDRESS] (H.H. ); [EMAIL_ADDRESS] (C.K. ); [EMAIL_ADDRESS] (S.R.) [PERSON]  
1 Department of Prosthodontics and Biomaterials, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany; [EMAIL_ADDRESS] (H.H. ); [EMAIL_ADDRESS] (C.K. ); [EMAIL_ADDRESS] (S.R.) [PERSON]  
2 Department of Oral and Maxillofacial Surgery, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany; [EMAIL_ADDRESS] (Correspondence: [EMAIL_ADDRESS] 20222022022022022022022022022022022022022022022202202220222022202220222022220222222222222222222222222222222222222222222222222222222222  
material extrusion, material jetting (MJ), and binder jetting (BJ) technologies as well as powder bed fusion technologies such as selective laser sintering or melting (SLS/M) [2; 3]. In vat polymerization, a photosensitive resin is polymerized layer by layer with light [4; 5]. DLP, as used in this study, cures one layer at a time using a light source, such as light-emitting diodes, covering wavelength ranges from deep ultraviolet to visible [5; 6]. SLA, on the other hand, cures one layer point by point using a coherent light source (usually an ultraviolet (UV) laser beam). CLIP differs from the other vat polymerization techniques in its oxygen-permeable membrane to inhibit radical polymerization at the surface close to the UV source [2; 5]. Material extrusion describes a technique in which thermoplastic materials are melted and extruded through a jet head forming objects by filament layering [7]. Jetting technologies extrude either a liquid photosensitive resin (material jetting) which is polymerized with UV light or a binder (binder jetting) [4; 8]. Binder jetting uses bonding agents to fuse powders. Selective laser sintering and melting work with a laser to sinter or melt and then fuse powdered materials such as polymers, metal, ceramic, or glass, which are applied layer-by-layer via rollers [3; 9]. The advantages of additive manufacturing are less material waste and nearly unlimited degrees of freedom in manufacturing compared to subtractive methods [1]. At the same time, it allows unlimited replica production and provides a wide range of indications such as the production of casts, surgical guides, occlusal splints, and temporary restorations [4; 10]. Printed resin casts show fewer abrasion, less fracture risk, and light weight [11]. Apart from that, model editing is virtually facilitated and quick data transfer to a dental laboratory or other practitioners is possible [12]. Printed casts are a feasible alternative for conventional gypsum casts regarding trueness and precision. However, the staircase effect is undeniable due to the layer-by-layer approach of vat polymerization methods. There are two main causes for this effect, one of them being the geometric approximation of a curved surface by layers with uniform thickness and the second one being material shrinkage of each individual layer while printing [13]. For staircase control, layer thickness should be decreased [13]. Staircases were reported to cause a dimensional error and poor surface roughness resulting in additively manufactured objects unacceptable for many indications [14]. For tasks such as waxing, printed casts are not necessarily usable. For 3D printing, the environmental impact, printing time, and cost are other important topics in comparison with conventional manufacturing. Environmental factors such as resource consumption, material waste, and energy consumption either by the 3D manufacturing process itself or due to disposal cannot be neglected [15]. Next to energy consumption, costs are influenced by the acquisition cost of the printer solution and running costs for resin, gas, and isopropyl alcohol. Printing time can be reduced by the orientation of the object on the building platform.