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 (<12 MPa). Failure mode analysis showed predominantly mixed/cohesive failures in high-SBS groups and adhesive failures in low-SBS groups.

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.