Mechanical analysis of 3D printed dental restorations produced from different resins

Objective: The aim of this study was to compare the wear and fracture resistance of single crowns produced from newly developed 3D printer resins used to produce permanent crowns and currently used composite CAD/CAM discs, after being thermomechanically aged for 2 years in a chewing simulator. Materials and Methods: Steel stump models imitating teeth number 36 were produced, 8 for each group (total = 112 pieces). The models were scanned with a scanning device. Single crowns were produced from 3 different discs (Grandio Voco [GV], breCAM HIPC [HC] and Shofu HC [SF]) by milling method. Single crowns were produced from 4 different permanent composite resins (Nexdent C&B MFH [N], Permanent Bridge Saremco [S], VarseoSmile Crownplus [VS], Şenertek P-Crown [PC]) using the 3D printing method. All samples were scanned with an intraoral scanner (Sirona PrimeScan, Dentsply Sirona, Bensheim, Germany) to evaluate the volumetric loss that would occur in the samples. The single crowns forming the experimental group were thermomechanically aged in a chewing simulator with 49 N vertical occlusal force, 5-55 degree thermal cycle, 30s-30s waiting time, 1 mm vertical, 2mm horizontal movement and 400,000 cycles to simulate 2 years of chewing. To determine physical volume loss, 3D scans were repeated and calculated using the overlapping method. Compression test was applied to all samples with a universal testing device. After the test, imaging was performed using a stereomicroscope and scanning electron microscope (SEM) to evaluate the fracture morphology on the surface of the samples. Finite Element Method (FEM) analyzes were performed. SPSS 22 statistical program was used to perform statistical analyses. The findings were interpreted with statistical significance at the p<0.05 level. Results: As a result of thermomechanical aging, it was determined that there was a statistically significant difference between the groups in wear and fracture resistance (p<0.05). The highest amount of wear was found in the PC group, and the lowest amount of wear was found in the VS group. As a result of the compression test, the mean max fracture force was in the GV group and the mean min fracture force was seen in the PC group. Conclusion: When the results were evaluated, the crowns in all groups produced by milling and 3D printing provided acceptable in vitro wear and fracture resistance for clinical application. However, the wear and fracture resistance of resin-based materials should be supported by clinical studies. Keywords: Additive manufacturing, CAD-CAM, Chewing simulation, Crown, Milling, Resin