Influence of fabrication techniques and artificial aging on the fracture resistance of different cantilever zirconia fixed dental prostheses.

Abstract

To evaluate the influence of dynamic fatigue on fracture load and failure mode of different types of adhesive zirconia restorations. Eighty adhesive cantilever fixed dental prostheses (CFDP) were fabricated and assigned to four equal groups (n = 20) using the following materials and techniques. Group 1: machine copy-milling zirconia (Cercon), group 2: manual copy-milling technique (ZirkonZahn), group 3: slip casting technique (Vita In-ceram Zirconia), group 4: metal-ceramic CFDP. Specimens in groups 1and 2 received selective infiltration-etching surface treatment, specimens in group 3 were acid etched with hydrofluoric acid and silanated, while those of group 4 were airborne particle abraded. All specimens were bonded with resin cement (Panavia F2.0) and thermocycled (5000 cycles/ 5 to 55°C). Then, half the number of the specimens of each group (n = 10) underwent dynamic loading (one million cycles at alternating loads between 10 and 40 N in a water bath at 37°C). All specimens were subjected to one-cycle loading to failure to evaluate fracture resistance. One-way and two-way ANOVA and Bonferroni post-hoc tests were used to analyze the data (α = 0.05). The intaglio surfaces of fractured specimens were examined using stereomicroscopy and scanning electron microscope (SEM). Statistical analysis revealed that the failure load of metal (413 ± 26 N) and machine copy-milled zirconia (368 ± 24 N) restorations was significantly higher (F = 129, p < 0.001) than manually copy-milled (316 ± 18) and In-ceram zirconia (210 ± 17) restorations. Dynamic fatigue significantly (p < 0.03) reduced failure load of the manually copy-milled and In-ceram zirconia restorations, while metal and machine copy-milling zirconia restorations were not influenced by fatigue. The fatigue strength of adhesive zirconia restorations is influenced by cyclic loading and the technique used to manufacture these restorations.