The effect of hydrofluoric acid concentration on the fatigue failure load of adhesively cemented feldspathic ceramic discs

Objective. This study investigated the influence of hydrofluoric acid (HF) etching at different concentrations on the fatigue failure load of adhesively cemented feldspathic ceramic discs (Vita Mark II). Besides, their effect on the micromorphology of ceramic surface was investigated. Methods. Eighty ceramic discs (phi = 10 mm; thickness = 1.5 mm) were cemented to epoxy supporting discs (phi = 10 mm; thickness = 2.0 mm) using different surface conditioning methods (n = 20): nonetched control (CTRL), or etched for 60 s with different HF concentrations: 1% (HF1), 5% (HF5), or 10% (HF10). All the ceramic discs received a silane application (Monobond Plus). The epoxy discs were etched with 10% HF for 60 s and received a primer coating (Multilink Primer A + B). Adhesively cementation was performed (Multilink Automix), and the assemblies (ceramic discs/epoxy discs) were subjected to cyclic loads in water by a staircase approach (500,000 cycles; 20 Hz; initial load = 290 N; step size = 30 N). Fatigue failure load data were analyzed using 1-way ANOVA and post-hoc Tukey's tests (alpha =.05). Results. Mean failure load of the HF5 group (255.0 +/- 23.0 N) was significantly lower; HF1 group (301.7 +/- 71.0 N) presented intermediate values, and the highest values were achieved in CTRL (351.7 +/- 13.4 N) and HF10 (341.7 +/- 20.6 N) groups. All the failures were radial cracks starting from the bonding surface. (C) 2018 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.