Microshear Bond Strength of Lithium Disilicate Acid Etching With Different Protocols

Objectives: The purpose of this study was to evaluate the microshear bond strength of a resin cement to a lithium disilicate glass ceramic after acid etching with 5% and 10% hydrofluoridric acid (HF) and 20 and 60 seconds of application time.
Methods: Sixteen specimens of lithium dissilicate with standard size (10 x 2 mm) were divided into four groups according to the application: G1 - application of 10% hydrofluoric acid for 20s; G2 - application of 10% hydrofluoric acid for 60s; G3 - application of 5% hydrofluoric acid for 20s; G4 - application of 5% hydrofluoric acid 5% for 60s. All blocks were silanized and received an adhesive layer. For the microshear bond test, six resin cement cylinders were built on the conditioned surface of each ceramic. After photopolymerization, the samples were subjected to axial loading in a universal testing machine. Data were analyzed using two-way ANOVA and Sidak post hoc test (p ≤ 0.05).
Results: There was no statistically difference between the conditioning times (20s and 60s) for both 5% (p=0.504) and 10% concentrations (p=0.077). A significance higher bond strength was observed for 10% HF (20,12 MPa) compared to 5% HF (13,13 MPa) when the conditioning was carried out for 60s (p<0.001). For 20s of conditioning there was no statistically difference between G1 and G3 (p=0.14).
Conclusions: Acid etching with 10% HF for 60s showed higher bond strength compared to 5% HF. However, further investigations are needed to analyze the degree of matrix degradation and fragility of the restorations.