Comparison between different fracture toughness techniques in zirconia dental ceramics

Abstract Vickers indentation (IF) and single‐edge‐V‐notched beam (SEVNB), to measure the fracture toughness (K IC ) of zirconia‐based dental ceramics and mathematical models were proposed to establish a correlation between both. Zirconia (ZrO 2 ) stabilized with 3 mol. % of Y 2 O 3 (3Y‐TZP) and 5 mol% of Y 2 O 3 (5Y‐PSZ) were compacted ( n = 42) and sintered for 2 h at different temperatures (1475°C, 1500°C, 1550°C, or 1600°C). After sintering, they were characterized by relative density using the ASTM C373‐88 standard, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The average grain size was measured according to the ASTM E1382‐97 standard. The fracture toughness (K IC ) was determined using two methods: Vickers indentation fracture toughness (K IC ‐IF ): method based on mathematical modeling that considers the parameters used for the Vickers hardness test and Fracture toughness by the single‐edge‐V‐notch‐beam (K IC ‐SEVNB ): method proposed by ISO 23146:08. The main phases of the 3Y‐TZP and 5Y‐PSZ ceramics were ZrO 2 ‐tetragonal and ZrO 2 ‐cubic, respectively. The 3Y‐TZP specimens showed equiaxed grains with average grain sizes ranging from 0.55 to 0.79 μm. The grain sizes of 5Y‐PSZ of specimens sintered at 1475°C and 1600°C were 0.62 and 2.32 μm, respectively. For all ceramics the crack size ratio was c/a < 2.5, suggesting a Palmqvist‐type crack system. The fracture toughness measured by the Vickers indentation method (K IC ‐IF ) and by the SEVNB method (K IC ‐SEVNB ) was the same when the experimental data were fit to a mathematical model.