Comparison of two fracture toughness testing methods using a glass-infiltrated and a zirconia dental ceramic

Abstract

PURPOSE

The objective of this study was to compare the fracture toughness (K _Ic) obtained from the single edge V-notched beam (SEVNB) and the fractographic analysis (FTA) of a glass-infiltrated and a zirconia ceramic.

MATERIALS AND METHODS

For each material, ten bar-shaped specimens were prepared for the SEVNB method (3 mm × 4 mm × 25 mm) and the FTA method (2 mm × 4 mm × 25 mm). The starter V-notch was prepared as the fracture initiating flaw for the SEVNB method. A Vickers indentation load of 49 N was used to create a controlled surface flaw on each FTA specimen. All specimens were loaded to fracture using a universal testing machine at a crosshead speed of 0.5-1 mm/min. The independent-samples t-test was used for the statistical analysis of the K _Ic values at α=0.05.

RESULTS

The mean K _Ic of zirconia ceramic obtained from SEVNB method (5.4 ± 1.6 MPa·m ^1/2) was comparable to that obtained from FTA method (6.3 ± 1.6 MPa·m ^1/2). The mean K _Ic of glass-infiltrated ceramic obtained from SEVNB method (4.1 ± 0.6 MPa·m ^1/2) was significantly lower than that obtained from FTA method (5.1 ± 0.7 MPa·m ^1/2).

CONCLUSION

The mean K _Ic of the glass-infiltrated and zirconia ceramics obtained from the SEVNB method were lower than those obtained from FTA method even they were not significantly different for the zirconia material. The differences in the K _Ic values could be a result of the differences in the characteristics of fracture initiating flaws of these two methods.