## 2 Materials and Methods
### Crown Fabrication  
Three different layer thicknesses (20 \(\upmu\)m, 50 \(\upmu\)m, and 100 \(\upmu\)m) were used to print the crowns (\(n=10\) per layer thickness). First, the RS-STL file of the crown was imported to DLP software (MoonRay S100, SprintRay Inc, Los Angeles, CA, USA) to arrange the build angle and support configuration. As recommended by the manufacturer of the printing resin material (Nextdent Crown and Bridge Micro Filled Hybrid-MFH, C&B; 3D systems, Soesterberg, The Netherlands), the occlusal surface of the crown was angled 45\({}^{\circ}\) from the print area for improved occlusal surface details. The semiautomatically created support structures were checked and supports that were automatically created on the margin area and fitting surfaces of the crowns were manually eliminated. Then, this configuration was duplicated 10 times and 10 identical crown configurations were arranged in the build platform of the DLP printer (MoonRay S100 Software, SprintRay Inc, Los Angeles, CA, USA) to print all crowns in the same configuration. This configuration was further saved for 3 different layer thicknesses to print the crowns in identical configuration, but by using different layer thicknesses. The crowns were printed with the DLP printer (MoonRay S100, SprintRay Inc, Los Angeles, CA, USA) and an interim printing resin material (N1 shade, Nextdent Crown and Bridge Micro Filled Hybrid-MFH, C&B; 3D systems, Soesterberg, The Netherlands, Lot: XH312N21) by using 20 \(\upmu\)m, 50 \(\upmu\)m, or 100 \(\upmu\)m (\(n=10\)) layer thickness. According to the manufacturer, the printing material has 100-130 MPa flexural strength, 2400-2600 MPa flexural modulus, \(\leq\)70 \(\upmu\)g/mm\({}^{3}\) sorption, and \(\leq\)15.5 \(\upmu\)g/mm\({}^{3}\) solubility.  
Figure 1: Mandibular right first molar preparation.  
The DLP printer has UV DLP projector, LED-based light source, and 405 nm blue-violet light resin curing unit. After printing, the printed crowns were removed from the platform by using a putty knife, ultrasonically rinsed for 5 min (first 3 min then 2 min) in 96% clean alcohol solution (Alcohol isopropilico, [PERSON], Mexico City, Mexico) according to the manufacturers' recommendations. After ensuring that the crowns were dry and free of alcohol residue, they were postpolymerized by using an ultraviolet polymerizing unit (SprintRay Procure Model SRIP1811A, SprintRay Inc, Los Angeles, CA, USA) (405 nm LED arrays) for 30 min (Figure 2).  
The support structures were cut and trimmed after cooling and the surface was gently smoothened to prevent errors during the alignment procedure.  
In the milling technique, crowns were milled (Wieland Zenotec mini, V6.12.04, Wieland Dental + Technik GmbH & Co.KG, Pforzheimer, Germany) from a polymethyl methacrylate (PMMA) block (A2 shade, Lot number: HI201104, Upcera, Shenzhen Upcera Dental Technology Co. Ltd., Shenzen, Guandong, China). The designed STL file was inserted in the block to mill 10 identical crowns. The support structures were cut and trimmed after milling, and the support surfaces were gently smoothened. All crown fabrication processes were performed by one operator ([PERSON]).  
Figure 2: 3D-printed interim crowns (**(A)**: 20 \(\upmu\)m crowns; **(B)**: 50 \(\upmu\)m crowns; **(C)**: 100 \(\upmu\)m crowns).