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: 150 bars (8 × 2 × 2 mm) and 100 blocks (8 × 8 × 2 mm) were made and divided into 5 groups, according to two factors: "material" (AR: acrylic resin, CR: composite resin, BIS: bis-acryl resin, CAD: CAD/CAM resin, and PRINT: 3D-printed resin) and "aging" (non-aged and aged - TC). Half of them were subjected to thermocycling (10,000 cycles). The bars were subjected to mini-flexural strength (σ) test (1 mm/min). All the blocks were subjected to roughness analysis (R_a/R_q/R_z). The non-aged blocks were subjected to porosity analysis (micro-CT; n = 5) and fungal adherence (n = 10). Data were statistically analyzed (one-way ANOVA, two-way ANOVA; Tukey's test, α = 0.05).

Results: For σ, "material" and "aging" factors were statistically significant (p < 0.0001). The BIS (118.23 ± 16.26^A) presented a higher σ and the PRINT group (49.87 ± 7.55^E) had the lowest mean σ. All groups showed a decrease in σ after TC, except for PRINT. The CR_TC showed the lowest Weibull modulus. The AR showed higher roughness than BIS. Porosity revealed that the AR (1.369%) and BIS (6.339%) presented the highest porosity, and the CAD (0.002%) had the lowest porosity. Cell adhesion was significantly different between the CR (6.81) and CAD (6.37).

Conclusion: Thermocycling reduced the flexural strength of most provisional materials, except for 3D-printed resin. However, it did not influence the surface roughness. The CR showed higher microbiological adherence than CAD group. The BIS group reached the highest porosity while the CAD group had the lowest values.

Clinical relevance: 3D-printed resins are promising materials for clinical applications because they have good mechanical properties and low fungal adhesion.

Keywords: 3D-printed resin; Aging; Biofilm; CAD-CAM; Flexural strength; Provisional material.

Fig. 1

Specimen preparation and obtaining of the mini bars from the silicone mold. AR acrylic resin, BIS bis-acryl, CR composite resin, CAD CAD/CAM resin, and PRINT 3D-printed resin. Graphic abstract elaborated by the authors

Fig. 2

Flowchart of the study design

Fig. 3

Weibull plot for flexural strength

Fig. 4

Micro-CT analysis of two-dimensional images for the resin groups. A Acrylic resin (AR), B composite resin (CR), C bis-acryl resin (BIS), D CAD-CAM resin, and E print resin (PRINT). The porous in the specimen showed radiolucent areas similar to the black arrows. The cerium nitrate appear as radiolucent areas similar to the black arrows. The cerium nitrate appear as radiopaque areas similar to the white arrows

Fig. 5

Mean log (CFU/mL) of Candida albicans (ATCC90028) cultivated on the specimens (mean and SD). *Different lowercase indicated statistically significance (p < 0.05; ANOVA, Turkey)