The Effect of Different Surface Treatments and Thermocycling on Repair Bond Strength of a 3D-Printed Permanent Crown Resin

Abstract

The aim of this study was to investigate the effects of surface treatments and thermocycling on the shear bond strength of a 3D-printed permanent crown resin. A total of 120 disc-shaped specimens (10 × 3 mm) were fabricated using a 3D printer and randomly assigned to four groups according to surface repair protocols: airborne-particle abrasion with Al2O3, bur roughening, 37% orthophosphoric acid etching, and a control group with no surface treatment. All specimens received a silane coupling agent followed by an adhesive resin application, and repair was performed using a highly filled flowable composite. Each group was divided into three subgroups and subjected to 1000, 5000, or 15,000 thermal cycles. Shear bond strength was measured, failure modes were analyzed, and data were evaluated using two-way ANOVA and Tukey’s post hoc test (p < 0.05). The sandblasting group exhibited the highest bond strength (18.7 ± 5.0 MPa), which was significantly higher than the control (12.6 ± 3.7 MPa) and acid-etching (14.2 ± 3.8 MPa) groups (p < 0.05). Aging periods had no significant effect on bond strength (p > 0.05). Additionally, the interaction between surface treatment and thermocycling had no significant effect (p = 0.823). Under the tested conditions, airborne-particle abrasion resulted in the highest shear bond strength of 3D-printed permanent crown resin.