Comparison of low-pressure plasma and standard surface conditioning on lithium disilicate and zirconia ceramics: An in vitro study

This study aimed to evaluate the influence of low-pressure oxygen and argon plasma treatments compared to conventional surface conditioning methods on ceramics' wettability, bond strength, and surface characteristics. Cylindrical specimens of lithium disilicate (LS2) and zirconia (ZR) were divided into three groups (n = 10 per group): control (hydrofluoric acid etching for LS2 and sandblasting for ZR), oxygen plasma, and argon plasma treatments. Plasma treatments were performed in a low-pressure system. Wettability was assessed by contact angle measurements using the sessile drop method, while bond strength was tested by shear bond strength (SBS) following thermocycling. Surface characteristics were analyzed using Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. Statistical analyses included ANOVA, Kruskal-Wallis, Student's t-test, and Mann-Whitney U test, with significance set at P ≤ 0.05. Plasma treatments significantly enhanced the wettability of both ceramics compared to controls ( p < 0.05). In LS2, the control group presented the highest contact angle values (50.07 ± 2.70°), while the oxygen plasma group had the lowest (12.97 ± 2.16°; p < 0.001). Similarly, in ZR, the control group exhibited the highest contact angle (55.00 ± 5.96°), and the argon plasma showed the lowest (14.75 ± 2.26°; p < 0.001). No significant differences in SBS were found among LS2 groups ( p = 0.51). In ZR, the oxygen plasma group exhibited the highest SBS (21.32 ± 1.85 MPa), significantly greater than the control (13.37 ± 1.88 MPa; p = 0.018). Low-pressure oxygen and argon plasma treatments significantly improved the wettability of lithium disilicate and zirconia ceramics. Plasma treatment significantly enhanced bond strength only in zirconia compared to conventional methods. Low-pressure plasma treatments significantly enhance the surface wettability and chemical activation of lithium disilicate and zirconia ceramics, potentially improving the reliability of adhesive bonding, especially for zirconia.