Simplified method for determining fracture toughness of two dental ceramics

Abstract

This study compared the fracture toughness values (KIC), which were derived from simplified techniques: the indentation fracture (IF), the indentation strength (IS), and fractographic approach to that from a standard testing using surface cracks in flexure (SCF). Forty bar specimens, twenty IPS Empress ® Esthetic and twenty IPS e.max ® Ceram were prepared. Ten specimens in each material were tested by IF technique, IS technique and fractographic approach, and additional 10 specimens were tested by the SCF technique. This study showed that the mean KIC derived from fractographic approach were not significantly different from that of the SCF in both materials (p>0.05) whereas the mean KIC from indentation techniques rarely agreed with those of the standard technique. The KIC determination is sensitive to the methods used that affect accuracy. Consequently, test selection should be based on a sound understanding and inherent limitations of each technique.

Fracture toughness of different monolithic zirconia upon post-sintering processes

“…The IF method is a simple and non-destructive technique that frequently uses when the material possesses high hardness or high strength ( 19 ). The selection of proper load is crucial to prevent forming crack branches and chipping of the material surface ( 17 , 19 ).…”

“…The crack lengths are in an inverse proportion to the toughness of the material ( 15 , 18 ). The indentation load was different for each material, so, the optimum load should verify and beforehand ( 16 , 17 ). Since the post-sintering processes of monolithic zirconia are unavoidable procedures.…”

Numerical Simulation of the Depth-Sensing Indentation Test with Knoop Indenter

“…Hardness tests with the Knoop indenter have been valuable in the mechanical characterization of some materials, such as thin coatings [6,7] and biological materials (e.g., dental tissue [8]). Another important application of this hardness tests is in the field of the gradient materials obtained by severe plastic deformation (see, e.g., [9][10][11]), for which it is required to determine the mechanical properties in thin samples and/or thin surface layers of the samples.…”