Evaluation of the optical and mechanical properties of conventional and digital acrylic resins

Recent advancements in digital technologies have enabled the use of CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) systems in the fabrication of complete dentures. Digitally produced dentures offer several advantages, such as reducing appointment times, preventing polymerization shrinkage in pre-polymerized blocks, and minimizing microbial contamination. Ensuring the cleanliness of complete dentures used by patients is important for maintaining oral health. Therefore, it is expected that the denture base materials exhibit desirable physical properties and color stability. The aim of this study was to compare the physical and optical properties of denture base materials prepared using two different digital methods with those produced by the conventional heat-polymerized PMMA technique. For each group, n=12 specimens were fabricated and subjected first to coffee staining and then to a denture cleansing agent. After these treatments, surface roughness, water sorption, and color changes were investigated. Surface roughness was measured using a contact profilometer, water sorption was determined with a precision balance, and color measurements were performed with a colorimeter. Regarding surface roughness, statistically significant differences were found between the 3D-printed group and the conventional and subtractive groups after coffee staining (p<0.001 and p=0.038, respectively). The measurements for the conventional and subtractive groups were higher than those of the 3D group. In water sorption analyses, the interaction effect of time and group was not significant (p=0.641), indicating no significant differences between measurements taken at different times (p>0.05). In terms of color measurement, statistically significant differences were observed at baseline between the 3D-printed group and both the conventional and subtractive groups (p<0.001 for both). According to the post-cleaning tests, statistically significant differences were also found between the 3D-printed group and the conventional and subtractive groups (p<0.001 and p=0.033, respectively). The color change values for the 3D group were higher than those for the conventional and subtractive groups. The application of a denture cleansing agent after coffee staining was not sufficient to prevent discoloration for the 3D-printed denture base materials.