Background: This study evaluated the surface morphology, chemical composition and adhesiveness of lithium disilicate glass ceramic after acid etching with hydrofluoric acid or phosphoric acid.
Methods: Lithium disilicate glass ceramic specimens polished by 600-grit silicon carbide paper were subjected to one or a combination of these surface treatments: airborne particle abrasion with 50-mu m alumina (AA), etching with 5% hydrofluoric acid (HF) or 36% phosphoric acid (Phos), and application of silane coupling agent (Si). Stainless steel rods of 3.6-mm diameter and 2.0-mm height were cemented onto treated ceramic surfaces with a self-adhesive resin cement (Clearfil SA Cement). Shear bond strengths between ceramic and cement were measured after 24-hour storage in 37 degrees C distilled water.
Results: SEM images of AA revealed the formation of conventional microretentive grooves, but acid etching with HF or Phos produced a porous surface. Bond strengths of AA+HF+Si (28.1 +/- 6.0 MPa), AA+Phos+Si (17.5 +/- 4.1 MPa) and HF+Si (21.0 +/- 3.0 MPa) were significantly greater than those of non-pretreated controls with Si (9.7 +/- 3.7 MPa) and without Si (4.1 +/- 2.4 MPa) (p<0.05). In addition, HF etching alone (26.2 +/- 7.5 MPa) had significantly higher bond strength than AA alone (11.5 +/- 4.0 MPa) (p<0.05). AA+HF, AA+Phos and HF showed cohesive failures.
Conclusions: Etching with HF or Phos yielded higher bond strength between lithium disilicate glass ceramic and self-adhesive resin cement without microcrack formation.