Adhesion of resin composites to 3D-printed dental resins: A study on the effect of surface conditioning methods and repair materials

PURPOSE: To evaluate the adhesion of 3D-printed dental resins according to surface conditioning protocol, repair material, and aging condition. METHODS: Disc-shaped specimens (10 mm × 2 mm) were fabricated from a 3D-printed resin for definitive restorations (Crowntec, Saremco Dental AG). The study design included 36 groups (n = 10): 9 surface treatments, 2 repair materials (flowable composite or 3D-printed resin), and 2 aging conditions (before/after thermocycling). Repairs were performed using a hydrophobic adhesive resin (Heliobond). SBS was measured using a universal testing machine, and failure modes were analyzed under stereomicroscopy. Data were analyzed using three-way ANOVA and Tukey's post hoc tests (α = 0.05). RESULTS: Surface treatment (p < 0.001) and repair material (p < 0.001) significantly influenced SBS, whereas aging showed no significant effect (p = 0.539). Tribochemical silica coating + primer and aluminum oxide air abrasion + primer yielded the highest SBS values (>25 MPa), particularly for 3D-printed resin repair (up to 31.27 ± 4.75 MPa). Minimal surface conditioning protocols resulted in significantly lower SBS values (