Comparison of the indentation strength and single-edge-v-notched beam methods for dental ceramic fracture toughness testing

Abstract

Aim: To study influence of the cooling rate after sintering a veneering porcelain (Vita VM9) on fracture toughness by indentation strength (IS) and single-edge-v-notched beam (SEVNB) methods. Methods: Vita VM9 bars were sintered according to the manufacturer’s recommendation and cooled under three conditions: Slow (inside the furnace from sintering temperature to room temperature); Normal (inside the furnace from sintering temperature to 500 ºC and outside the furnace from 500 ºC to room temperature); and Fast (outside the furnace from sintering temperature to room temperature). Fracture toughness was measured by IS (n=10) and SEVNB (n=10) methods. Data were analyzed by two-way ANOVA (α=0.05). Results: The fracture toughness obtained from SEVNB (slow - 1.02±0.10; normal - 1.09±0.13; and fast - 1,02±0.18 MPa.m1/2 cooling techniques) was significantly lower than IS (slow - 1.19±0.13; normal - 1.17±0.07; and fast - 1.16±0.06 MPa. m1/2 cooling techniques). There was no significant influence of the cooling technique (p=0.012). Conclusions: The measurement technique influenced the fracture toughness values . IS method overestimated the fracture toughness values. Irrespective of the measuring method, cooling rate did not influence the Vita VM9 veneering porcelain fracture toughness.

Effect of barium iron tantalate incorporation on mechanical, electrical, and magnetocapacitance properties of modified bismuth sodium potassium titanate ceramics

“…where P = load (N) and d = half-length of long diagonal (µm). The E and K IC values were also calculated using the following equations: [24,26]…”

Fracture toughness of three heat pressed ceramic systems

“…However, the fracture toughness results are lower than results of other study that evaluated the same ceramic 8 . This difference is probably caused by the difference of the method used to evaluate fracture toughness because the previous study used single edge notched beam method 8 and there is difference in the results of fracture toughness evaluated by different methods 15,24 . The same difference was noted for fluorapatite glass ceramic (ZIR=0.977MPa/m) that presented lower fracture toughness in the present study than in the study mentioned before 8 .…”

“…This method was chosen because it is fast and permits measuring cracks in a small sample. Although there is difference in the results of fracture toughness evaluated by different methods 15,24 , this study aimed to compare fracture toughness of three ceramics using the indentation method. Fracture toughness measured by indentation method is related to hardness and elastic modulus.…”

Energy harvesting, electrical, and magnetic properties of potassium bismuth titanate-based lead-free ceramics

“…Fracture toughness (K IC ) was also determined from the length of the cracks that propagated from the four corners of indentation impression, following the method described by Meredith et al [32]. The E and K IC values were also calculated using the following formula [49][50][51]: contributed to both improvements of densification and the reduction of grain size, where the higher density but lower grain size can give rise to better mechanical properties (Figure 6(a) [53]. From the study of E and K IC values in Figure 6(c), it was found that these values depended on composition and their trends followed that of the trend of hardness value.…”