Flexural strength, surface roughness, micro-CT analysis, and microbiological adhesion of a 3D-printed temporary crown material

Abstract Objective: To evaluate the thermocycling effect of 3D-printed resins on flexural strength, surface roughness, microbiological adhesion, and porosity. Materials and methods: Specifically, 150 bar specimens (8 × 2 × 2 mm) and 100 blocks (8 × 8 × 2 mm) were made and divided among five groups, according to two factors: “material” (AR: acrylic resin, CR: composite resin, BIS: bis-acryl resin, CAD: CAD/CAM PMMA resin, and PRINT: 3D-printed resin) and “aging” (non-aged and aged – TC). Half of the samples from each group were subjected to thermocycling (10,000 thermocycles; 5–55 °C), and the rest were stored in water (37 ºC) for 24 h. The bars were then subjected to a mini flexural strength (σ) test (1 mm/min; 100kgF). All the blocks were subjected to roughness values (Ra, Rq, and Rz). The non-aged blocks were subjected to porosity analysis (micro-CT (n=5)) and fungal adherence (n=10). The data of σ (MPa) and Ra, Rq, and Rz(µm) were statistically analyzed using two-way ANOVA and Tukey’s test. Weibull analysis was performed to verify the reliability of the σ data. Fungal adhesion (log CFU/mL) data were analyzed using one-way ANOVA and Tukey’s test. Results: For flexural strength, ANOVA showed that “material” and “aging” factors were statistically significant (p<0.0001). The mean flexural strength ranged from 49.87 MPa to 118.23 MPa between the experimental groups. The BIS group (118.23±16.26A) presented higher σ value than the AR group (89.60±9.38BC), whereas the PRINT group (49.87±7.55E) had the lowest mean of the flexural strength (Tukey, a=0.05). All groups showed a decrease in σ after thermocycling, except for the PRINT group, which showed significantly increased flexural strength after aging (PRINTTC:81.33±20.38CD). The Weibull modulus for the CRTC was significantly lower than those of the other groups. The AR group showed higher roughness values than the BIS group, regardless of age (p<0.0001). Porosity analyses revealed that the AR (1.369%) and BIS (6.339%) groups presented the highest porosity values among the experimental groups and that the CAD group (0.002%) had the lowest porosity. Cell adhesion was significantly different between the CR (6.81) and CAD (6.37) groups (p=0.036). Conclusion: Thermocycling reduced the flexural strength of most provisional materials evaluated, except for 3D-printed resin. However, it did not influence the surface roughness of each material. Moreover, Candida albicans adherence and porosity varied among materials. Clinical relevance: 3D-printed resins are promising materials for clinical applications because they have good mechanical properties and low fungal adhesion.