Effect of Acid Etching on Lithium Disilicate Glass Ceramic

Objectives: The purpose of this study was to evaluate the effect of two different types of acid etching on the bond strength of lithium disilicate glass ceramic (IPS e.max Press, Ivoclar) cemented with self-adhesive resin cement. Methods: IPS e.max Press specimens polished by 600-grit SiC paper were etched with 5% hydrofluoric acid (HF) or 36% phosphoric acid (PO), or air-abraded with 50 μm alumina. Each pretreated surface was cemented to a stainless steel rod of 3.6 mm diameter and 2.0 mm height with self-adhesive resin cement (Clearfil SA Cement, Kuraray) using a Teflon mold followed by the application of the ceramic primer (control+pri) or not (control-pri). Shear bond strength between ceramic and cement were measured after 24 h storage in 37°C distilled water. The microstructure morphology of the surface after pretreatment was evaluated using SEM analysis. Statistical analyses were performed by one-way ANOVA and Holm-Sidak test. Results: The bond strength of HF followed by AA (HF+AA, 28.1±6.0 MPa), PO followed by AA (PO+AA, 17.5±4.1 MPa), and HF (21.0±3.0 MPa) were significantly greater than that of control+pri (9.7±3.7MPa) or control- pri (4.1±2.4 MPa) (p<0.05). In addition, with HF or PO (14.0±2.5 MPa) the shear bond strength significantly increased over AA (13.2±3.7 MPa) (p<0.05). HF+AA, PO+AA and HF exhibited cohesive failure, while the others mainly exhibited adhesive failure. SEM images of AA showed formation of conventional microretentive grooves, but acid etching with HF or PO produced a porous surface. Conclusions: Hydrofluoric acid or phosphoric acid etching yields higher bond strengths between lithium disilicate ceramic and a self-adhesive resin cement without creating microcracks by air abrasion.