Influence of LiSi Ceramic Surface Cleaning Methods on Bond Strength

Objectives: To evaluate the effects of different cleaning protocols of LiSi CAD/CAM ceramic blocks on bond strength to resin cement.
Methods: CAD/CAM LiSi ceramic specimens (IPS e.max CAD – Ivoclar) were prepared (4x4x4mm) and contaminated with human saliva and try-in silicone paste. The following surface cleaning methods were investigated on ceramic surfaces pre-treated by the dental technician with hydrofluoric acid (HF) (n=10): 1) water rinsing (control, C); 2) 37% H₃PO₄ etching for 20s (PA); 3) 70% ethanol applied for 20s (E); 4) Ivoclean (Ivoclar) brushed for 20s (IVO); 5) Monobond etch&prime (MEP, Ivoclar) rubbed for 20s. Additional groups were formed on specimens not previously treated with HF in the laboratory: 6) HF applied for 20s (HF); 7) MEP rubbed for 20s (MEP2). A resin cement was bonded to the decontaminated surfaces and specimens stored for 24 h at 37 °C, before being submitted to the shear bond strength test and SEM evaluations. Data were statistically analyzed (p<0.05).
Results: The following significances were observed: MEP=MEP2=HF ≤ IVO≤ HP=E=C<0.05. SEM images showed detachments within the resin cement in the MEP, MEP2 and HF groups. Contamination residues were observed in the other groups. In particular, several traces of silicone material were present on the IVO-treated surfaces.
Conclusions: Cleaning LiSi CAD/CAM surfaces with one-component Monobond Etch&Prime resulted in higher bond strength between resin cement and ceramic blocks with/out HF pre-treatments.