## 2 Materials and Methods  
For designing the standard denture base, a fully dedentulous maxilla and mandible reference model was selected and then scanned using a tabletop scanner (Identica T500, Medit, Seoul, Korea). After importing the scanned model data into CAD software for dental use (Exocad DentalCAD, Exocad, Darmstadt, Germany), the denture base was designed, and the designed data were exported as an STL (standard tessellation language) file (Figure 1). Two types of 3D printing photocurable resin were used for the 3D printing of the design file: standard gray resin (Formlabs, Somerville, MA, USA) and MAZIC D resin (Vericom, Anyang, Korea) (Table 1). Each photocurable resin was mixed in accordance with the manufacturer's recommended mixing time using a material mixing unit (LC-3 DMixer, NextDent, Soesterberg, The Netherlands) to ensure that the contents were adequately mixed prior to printing. In order to optimally three-dimensionally print the material used, slicing software and a 3D printer with settings compatible with each photocurable resin were used. For printing MAZIC D resin, support generation and mesh slicing were performed using slicing software (Chitu DLP Slicer, CBD-Tech, Guangdong, China) for 3D printing. A support structure was placed on the outer surface of the denture base, and the thickness of each building layer was set to 100 \(\upmu\)m. Three-dimensional printing of the mesh file was performed using a DLP 3D printer with 24,405-nm UV LEDs in a 50-W matrix (ParalED, Pharozen Shuffle, Pharozen, Hsinchu, Taiwan). For the standard gray resin, the support arrangement design specified by the Chitu DLP Slicer software was imported into the Preform slicer software (Formlabs, Somervill, MA, USA) to make the same arrangement, and three-dimensionally printed using a compatible SLA 3D printer with a 250-mW 405-nm UV LED (Form3, Formlabs). Each manufactured denture base was washed with 100% isopropyl alcohol for 10 min using washing equipment (TwinTornado, Medifive, Seoul, Korea) and then postcured using a postcuring device (MP100, Hebsiba, Incheon, Korea). For the purpose of this study, the postcuring time and the removal of the support structure before the postcuring process were set differently for each group. In the no-support group, after 3D printing the denture base, the support structure was removed prior to carrying out postcuring. For the support group, postcuring was performed without \begin{table}
\begin{tabular}{c c c} \hline \hline
**Product** & **Components** & **Manufacturer** \\ \hline Standard gray resin & 75–90\% methacrylic oligomers, 25–50\% methacrylate monomer, 1–3\% & Formlabs, Somerville, MA, USA \\  & 2,4,6-trimethylbenzoyll-diphenyl-diphenyl phosphine oxide & \\ \hline MAZIC D resin & 88–98\% ethoxylated bisphenol A dimethacrylate, 2–5\% & \\  & 2,4,6-trimethylbenzoyll-diphenyl-diphenyl phosphine oxide & Vericom, Anyang, Korea \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The three-dimensional-printing photopolymer resins used in this study. Figure 1: Designs of the experimental maxillary and mandibular denture bases. removal of the support structure after printing the denture base. In addition to a control group (with no postcuring), postcuring times of 15, 30, 45, and 60 min were employed (\(n=10\) for each denture base). Data relating to the denture base in all groups were obtained using 3D scanning with a tabletop scanner after postcuring. The overall experimental workflow employed in this study is outlined in Figure 2.  
All acquired data were exported to 3D analysis software (Geomagic Control X, 3D Systems, Rock Hill, SC, USA). To analyze the dimensional changes during postcuring of the denture base, the 3D modeling data and the scanned data after postcuring were compared and analyzed. The data to be compared were initially aligned using a three-point registration process and then further aligned using a best-fit algorithm.