Impact of plasma treatment of PMMA-based CAD/CAM blanks on surface properties as well as on adhesion to self-adhesive resin composite cements

Objectives To test surface energy, roughness and tensile bond strength (TBS) to self-adhesive resin composite cements without/with plasma treatment combined with different conditioning methods of PMMA-based CAD/CAM blocks. Methods PMMA specimens (10mm×10mm×2mm) were fabricated (N=260), polished and air-abraded (50μm Al2O3, 5s, 0.05MPa). Twenty specimens were selected for surface energy and roughness measurements (without/with plasma n=10 per group). The remaining specimens (n=240) were used for TBS testing without/with plasma treatment and following conditioning methods (n=20 per test group): (i) without conditioning, (ii) Visio.link, (iii) VP connect and luted with Clearfil SA Cement and RelyX Unicem Automix. Specimens were aged (24h 37°C water+5000 thermal cycles, 5°C/55°C), TBS was measured and failure types were assessed. Data were analyzed using descriptive statistics, Mann-Whitney-U and Kruskal-Wallis-H tests, unpaired t-test, Chi(2) and the Spearman correlation test. Results Plasma treatment of PMMA increased the surface energy significantly (p<0.001) but had no impact on the surface roughness (p=0.718). Groups without plasma treatment showed higher TBS than plasma treated groups (p<0.001 to p=0.011), except PMMA conditioned with VP connect and luted using RelyX Unicem Automix (p=0.03). Clearfil SA Cement showed higher TBS compared to RelyX Unicem Automix, except for groups conditioned with Visio.link. Both resin composite cements showed the highest TBS for groups conditioned with Visio.link. Also, among Clearfil SA Cement, conditioning with VP connect showed comparable TBS to Visio.link. Significance Plasma treatment of PMMA did not increase the adhesion to self-adhesive resin composite cements.