Effect of repair methods and materials on the flexural strength of 3D-printed denture base resin

Abstract

Purpose: The aim of this study was to evaluate the flexural strength of a 3D-printed denture base resin (Cosmos Denture), after different immediate repair techniques with surface treatments and thermocycling.

Materials and methods: Rectangular 3D-printed denture base resin (Cosmos Denture) specimens (N = 130) were thermocycled (5,000 cycles, 5℃ and 55℃) before and after the different repair techniques (n = 10 per group) using an autopolymerized acrylic resin (Jet, J) or a hard relining resin (Soft Confort, SC), and different surface treatments: Jet resin monomer for 180 s (MMA), blasting with aluminum oxide (JAT) or erbium: yttrium-aluminum-garnet laser (L). The control group were intact specimens. A three-point flexural strength test was performed, and data (MPa) were analyzed by ANOVA and Games-Howell post hoc test (α = 0.05). Each failure was observed and classified through stereomicroscope images and the surface treatments were viewed by scanning electron microscope (SEM).

Results: Control group showed the highest mean of flexural strength, statistically different from the other groups (P < .001), followed by MMA+J group. The groups with L treatment were statistically similar to the MMA groups (P > .05). The JAT+J group was better than the SC and JAT+SC groups (P < .05), but similar to the other groups (P > .05). Adhesive failures were most observed in JAT groups, especially when repaired with SC. The SEM images showed surface changes for all treatments, except JAT alone.

Conclusion: Denture bases fabricated with 3D-printed resin should be preferably repaired with MMA+J. SC and JAT+SC showed the worst results. Blasting impaired the adhesion of the SC resin.

Keywords: Dental prosthesis; Denture bases; Flexural strength; Printing; Resins; Three-dimensional.

Fig. 1. Description of groups. MMA: methyl methacrylate monomer of the Jet resin for 180 s; JAT: blasting with aluminum oxide 50 µm for 15 s; L: application of an erbium: yttrium-aluminum-garnet laser for 60 s.

Fig. 2. (A) Layout specimens planned on Adobe Meshmixer. (B) Software FlashDLPrint v. 3.28.0, printing orientation stablished in 0 degrees without support. (C) Flashforge printer - Hunter DLP Resin 3D Printer.

Fig. 3. Means of flexural strength (MPa) and standard deviations, according to the group (Games-Howell test, α = 0.05). Similar capital letters represent statistical similarity between different groups.

Fig. 4. Percentage of types of failure, according to the group.

Fig. 5. SEM photomicrographs of surface treatments with 12 kV and magnification of × 190. (A) no treatment, × 190; (B) Monomer for 180 s, × 190; (C) Blasting, × 190; (D) Laser, × 190; (E) Blasting + monomer, × 190; (F) Laser + monomer, × 190.