Evaluating the fracture toughness and flexural strength of pressable dental ceramics: an in vitro study.

The study was undertaken to evaluate the biaxial flexural strength, biaxial flexural strength after etching with 9 % HF acid and fracture toughness of three commonly used pressable all ceramic core materials. Ninety glass ceramic specimens were fabricated from three commercially available leucite based core ceramic material (1) Esthetic Empress, (2) Cergo, and (3) Performance Plus. Thirty discs of each material were divided into three groups of 10 discs each. Biaxial flexural strength (30 discs,) Biaxial flexural strength for samples treated with 9 % HF acid (30 discs) and fracture toughness (30 discs) were evaluated. Core material Performance Plus had the lowest biaxial strength of 124.89 MPa, Cergo had strength of 152.22 MPa and the highest value of 163.95 was reported for Esthetic Empress. For samples treated 9 % HF, Performance Plus had the lowest biaxial strength of 98.37 MPa, Cergo had strength of 117.42 MPa and the highest value of 143.74 was reported for Esthetic Empress. Core material Performance Plus had the lowest fracture toughness of 1.063 MPa, Cergo had strength of 1.112 MPa and the highest value of 1.225 was reported for Esthetic Empress. The results shows that Esthetic Empress had better mechanical properties compared to Cergo had Performance Plus in relation to the parameters tested.