Bond strength of resin cements to zirconia ceramics: Influence of micromechanical roughening and chemical etching

Purpose: The aim of this study was to evaluate the influence of combining sandblasting withchemical etching of zirconia surface on the shear bond strength at zirconia/resin cement interface.
Materials and methods:Ninety six zirconia discs were fabricated using CAD/CAM technologythen divided according to aluminum oxide particles size used for sandblasting (50 and 110 μm) into two main groups (n=48) then each main group divided according to NH₄HF₂ etching protocol (170⁰C for 10 min, 170⁰C for 20 min and 190⁰C for 10 min) to three subgroups (n=16). Zirconia discs were bonded to composite discs using resin cement (Multilink^®N). 8 specimens of each treatment group were stored in water bath for one week and the other 8 specimens stored in water bath for 6 months followed by 10,000 thermal cycles then all specimens underwent shear bond strength testing.
Results:Two Way ANOVAs test showed no statistical significant difference between the two
different aluminum oxide particles size used for sandblasting neither the different NH₄HF₂
etching protocols, after aging statistical significant difference appeared between different
NH₄HF₂ etching protocols P (≤0. 05). (110 μm + 170⁰C for 10 min) group had the highest mean
value of bond strength before aging (34.0±11.4). Bond strength values of all test groups badly
decreased after aging.
Conclusions:Combining sandblasting with chemical etching of zirconia surface providedsufficient bond strength to the resin cement that was badly affected after aging.
Clinical Significance:Etching zirconia surface by NH₄HF₂after sandblasting increased surfaceroughness improving bond strength with resin cement.