IADR Abstract Archives
Fatigue-failure-load of Lithium-disilicate Crowns Etched by Hydrofluoric Acid Concentrations
Objectives: To evaluate the influence of etching with hydrofluoric acid (HF) at distinct concentrations of the crowns’ inner surface on the fatigue failure load of lithium disilicate ceramic crowns.
Methods: Seventy-two simplified full-crown prosthetic preparations made in a dentin-like polymer material (NEMA G10) were machined and 72 simplified ceramic crowns (e-maxCAD, Ivoclar-Vivadent) (n=18) were milled by CAD/CAM (Cerec InLAB, Sirona). For crown cementation, the preparations were etched with 10% HF (60 s), and received a bonding agent (Multilink Primer A+B, Ivoclar-Vivadent). The intaglio surfaces of ceramic crowns were conditioned (randomly assigned: nonetched, or etched by HF3, HF5, or HF10 – etching for 20 s with 3%, 5%, and 10% HF, respectively), followed by bonding agent application (Monobond Plus, Ivoclar-Vivadent), and the crowns were adhesively cemented (Multilink Automix, Ivoclar-Vivadent). Afterward, monotonic fracture tests (n=3; HF10 group) by load application (hemispheric stainless steel piston with Ø=40mm) on the center of the crown were performed. The average from the monotonic tests (~1200N) was used for the parameters for fatigue tests by staircase approach (initial load of 720N (60% of the mean value); step-size of 70N (10% of initial load)), which was performed in the Instron Electropuls E3000 (Instron) (500,000 pulses per sample; 20Hz, under water), using the same piston. Fatigue failure load data were submitted to 1-way ANOVA and Tukey’s tests (α=.05). Topographic (etched surface) and fractographic (tested crowns) examinations were also performed.
Results: CTRL (790±78.3), HF3 (778.3±49.5) and HF10 (825±76.9) groups showed similar fatigue failure loads (in N). HF5 (755±90.6) had lower strength compared with HF10 only. Fractography findings show all the failures started from the intaglio surface of ceramic crowns. Voids (fails) without filing up by resin cement were observed for group HF5 only.
Conclusions: Etching with 5% hydrofluoric acid reduced the fatigue failure load of lithium disilicate crowns.
Methods: Seventy-two simplified full-crown prosthetic preparations made in a dentin-like polymer material (NEMA G10) were machined and 72 simplified ceramic crowns (e-maxCAD, Ivoclar-Vivadent) (n=18) were milled by CAD/CAM (Cerec InLAB, Sirona). For crown cementation, the preparations were etched with 10% HF (60 s), and received a bonding agent (Multilink Primer A+B, Ivoclar-Vivadent). The intaglio surfaces of ceramic crowns were conditioned (randomly assigned: nonetched, or etched by HF3, HF5, or HF10 – etching for 20 s with 3%, 5%, and 10% HF, respectively), followed by bonding agent application (Monobond Plus, Ivoclar-Vivadent), and the crowns were adhesively cemented (Multilink Automix, Ivoclar-Vivadent). Afterward, monotonic fracture tests (n=3; HF10 group) by load application (hemispheric stainless steel piston with Ø=40mm) on the center of the crown were performed. The average from the monotonic tests (~1200N) was used for the parameters for fatigue tests by staircase approach (initial load of 720N (60% of the mean value); step-size of 70N (10% of initial load)), which was performed in the Instron Electropuls E3000 (Instron) (500,000 pulses per sample; 20Hz, under water), using the same piston. Fatigue failure load data were submitted to 1-way ANOVA and Tukey’s tests (α=.05). Topographic (etched surface) and fractographic (tested crowns) examinations were also performed.
Results: CTRL (790±78.3), HF3 (778.3±49.5) and HF10 (825±76.9) groups showed similar fatigue failure loads (in N). HF5 (755±90.6) had lower strength compared with HF10 only. Fractography findings show all the failures started from the intaglio surface of ceramic crowns. Voids (fails) without filing up by resin cement were observed for group HF5 only.
Conclusions: Etching with 5% hydrofluoric acid reduced the fatigue failure load of lithium disilicate crowns.