Effect of Surface Treatments Applied to 3D Printed Permanent Resins on Shear Bond Strength.

Background: 3D-printed permanent resins have recently been introduced to produce permanent restorations. The aim of this study is to evaluate the effect of surface treatment methods on the shear-bond strength (SBS) between 3D-printed permanent resins and adhesive cement.

Material and methods: In this study, samples were produced using digital light projection (DLP) and stereolithography (SLA) 3D printers with two permanent resins (Crowntec, Saremco and Permanent Crown, Formlabs) in accordance with manufacturer guidelines. The samples were separated into three groups: sandblasting, hydrofluoric acid and no surface treatment. The surface profile (Ra, Sa) of the samples was examined with a confocal microscope (Smartproof 5, Zeiss). Then, a self-adhesive resin cement was applied to the samples in a transparent mold (2.38 mm diameter) in accordance with ISO 29022:2013. A universal testing machine was used to perform SBS test. A stereomicroscope was used to analyze the different types of fractures. A two-way analysis of variance (ANOVA) test was used to assess the data (p<0.05).

Results: The samples with sandblasting applied to the surface showed higher surface roughness values than the samples with hydrofluoric acid (p<0.001). 3D printer technology and surface treatment methods affected SBS values (p<0.001). Sandblasting groups higher SBS values were than in the hydrofluoric acid group (p<0.001). Sandblasting revealed cohesion fractures, which indicated a stronger bond, while hydrofluoric acid displayed adhesive and mix fractures.

Conclusions: When sandblasting was applied to the surface of the samples prepared using permanent resins, higher adhesion was achieved with adhesive cement. Key words:3D printing, Shear bond strength, Sandblasting, Stereolithography.