Fracture toughness determination of two dental porcelains with the indentation strength in bending method

Objective This study was to investigate the influence of the bending test configurations and the crosshead displacement speeds on the fracture toughness (KIc) of dental porcelains obtained with the indentation strength in bending (ISB) method. Methods The strength of the dental veneering porcelains Duceram and Sintagon Zx, Vickers’ indented at a load of 2 kg was measured at a crosshead speed of 0.5 mm/min with three test configurations, which were 3-point, 4-point, and biaxial bending. Two more groups of Sintagon Zx were tested the same way, but at speeds of 0.1, and 0.05 mm/min, respectively. Both porcelains, the three crosshead speeds, and the three test configurations were compared statistically. Results Duceram had a higher toughness than Sintagon Zx with all three test configurations and there was no significant difference between three test configurations with either porcelain. Within the crosshead speed groups of Sintagon Zx, a significant difference was found only in the 0.5 mm/min group between the 3-point, and 4-point configurations. Within the configuration groups, significant differences were found between all speeds with the 3-point configuration and only between the highest and lowest speed with the 4-point and the biaxial tests. Conclusion The crosshead displacement speed can cause statistically different results of fracture toughness obtained with the ISB method.