Effect of different surface treatments on surface roughness and flexural strength of repaired 3D-printed denture base: An in vitro study

Statement of problem. Information regarding three-dimensional-printed (3D-printed) dentures, especially when using the additive manufacturing technique, and the repair strength of this type of denture is sparse. Purpose. The purpose of this in vitro study was to assess the effect of different surface treatments on the surface roughness and flexural strength of repaired 3D-printed denture base. Material and methods. One hundred and twenty 3D-printed bar-shaped specimens were fabricated from acrylic resin and divided into 6 groups (n=20). The positive control group consisted of intact specimens. The other specimens were sectioned in half with a 1-mm gap. Except for the specimens in the negative control group, the remaining specimens were treated with erbium: yttrium-aluminum-garnet (Er:YAG) laser, airborne-particle abrasion, a combination of laser and airborne-particle abrasion, and bur grinding. All sectioned specimens were repaired by autopolymerizing acrylic resin and thermocycled after measuring their surface roughness with a profilometer. The flexural strength test was performed with a universal testing machine. One specimen of each group was inspected under a scanning electron microscope. The data were analyzed with ANOVA, followed by the Games-Howell post hoc test or the Kruskal-Wallis test followed by the Mann-Whitney test with Bonferroni adjustment. Results. The mean flexural strength of the PC group was significantly higher than that of all repaired groups (P<.001). All surface-treated groups showed significantly higher flexural strength (P<.05) and surface roughness (P<.004) than the negative control group. Bur grinding provided significantly higher flexural strength than other surface treatments (P<.001) and higher surface roughness than laser and airborne-particle abrasion plus laser (P<.001). Conclusions. All surface treatments significantly increased the surface roughness and flexural strength, but none of them yielded a strength comparable with that of the intact group. Bur grinding provided the highest flexural strength.