Efeito da concentração de ácido fluorídrico na carga para falha em fadiga de uma cerâmica feldspática cimentada

Abstract

The present thesis is composed by two scientific articles that evaluated the influence of different hydrofluoric acid concentrations on the fatigue failure loads of feldspathic ceramic crowns and discs adhesively cemented to a dentin analogue material (epoxy resin). Therefore, eighty crowns with simplified geometry and eighty feldspathic ceramic discs (Vita Mark II, Vita Zahnfabrik) were randomly allocated, and the intaglio surface of each crown/disc was treated with one of the four surface conditioning methods (n=20): nonetched / control (CTRL), or etched for 60 s with different hydrofluoric acid concentrations: 1% (HF1), 5% (HF5), or 10% (HF10). The treated ceramic surface received the application of a silane coupling agent. The cementation surface of simplified complete crown preparations and discs (both in epoxy resin) were etched with 10% hydrofluoric acid for 60 s and received a primer coating specific to the cementation system. After the surface treatments, the ceramic crowns and discs were adhesively cemented to the respective prosthetic preparations and epoxy resin discs, which were subjected to cyclic loads in water by a staircase approach (500,000 cycles, 20 Hz). Fatigue failure load data were analyzed by 1-way ANOVA and Tukey’s tests (α= .05). For the ceramic crowns, mean failure loads of groups CTRL (245.0 ± 15.1 N), HF1 (242.5 ± 24.7 N) and HF10 (255.7 ± 53.8 N) were statistically similar (P>.05), while the mean load of the HF5 group (216.7 ± 22.5 N) was significantly lower. In the condition of cemented discs, mean failure load of the HF5 group (255.0 ± 23.0 N) was also 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. Etching with 5% hydrofluoric acid had a deleterious effect on the fatigue failure loads of adhesively cemented feldspathic ceramic crowns and discs, while etching with 10% hydrofluoric acid had no negative influence in both tested conditions (crowns and discs).