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). Conclusions: Repair performance of 3D-printed resin was mainly influenced by surface conditioning. Mechanical surface treatment combined with primer showed the most promising bonding performance, whereas minimal conditioning protocols resulted in lower adhesion values. Thermocycling did not significantly affect SBS under the tested conditions. Clinical significance: Reliable repair of 3D-printed dental resins depends on adequate surface conditioning prior to adhesive procedures.