Comparative effects of plasma activation and monomer infiltration on the surface characteristics and wettability of 3D-printed permanent crown resin

Background/purpose The bonding performance of 3D-printed resins (3DRs) used for permanent crowns can be challenging due to their high filler content. This study evaluated the surface characteristics and wettability of non-thermal handheld plasma (NTHP) and resin-matrix penetrating primer (RMPP) treatments in comparison with conventional airborne-particle abrasion (APA) and universal adhesive (UA) protocols. Materials and methods Disc-shaped 3DR specimens were allocated into five surface-treatment groups: no treatment (NT), APA/UA (AU), APA/RMPP (AP), NTHP/UA (PU), and NTHP/RMPP (PP). Surface roughness and morphology were assessed. Wettability was determined by contact angle (CA) measurements using distilled water and diiodomethane, and surface energy (SE) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test (⍺ = 0.05). Results APA significantly increased surface roughness (P < 0.001), whereas NTHP produced no significantly topographical alteration compared with the control (P > 0.05). SEM analysis revealed that UA formed a granular surface layer, whereas RMPP created a smoother and continuous film that reduced roughness. All treatments significantly increased SE (P < 0.001). The UA groups achieved the highest total SE due to enhanced hydrophilicity; however, all treated groups demonstrated similarly low CAs with diiodomethane, suggesting that both bonding agents provide sufficient dispersive energy for hydrophobic resin interaction. Conclusion APA effectively modifies surface morphology, while NTHP activates the surface without altering its topography. Although UA yields the highest total SE, both UA and RMPP provide adequate dispersive energy to ensure favorable wetting by hydrophobic resin cements. Ultimately, the bonding agents effectively masked the mechanical topography, resulting in wettability driven primarily by the adhesive's chemical composition rather than the underlying mechanical pre-treatments.