Fracture toughness and flexural strength of dental ceramics for titanium.

Three brands of dental ceramics for veneering to titanium: TitanBond (O'Hara), Ti-Ceram (Ducera) and Titankeramik (Vita) were tested to compare their fracture properties in wet and in dry conditions. Eight polished and precracked specimens of each material were stored in water at 37 degrees C for 28 d and then preloaded in a four-point bending jig with a constant load of 50 N for 24 h under water. Five of the specimens were fractured by a four-point bending test also under water at 37 degrees C. Crack depths were measured in three different positions in each of the remaining three specimens. Fracture load and crack depths were used to calculate the fracture toughness. Another ten polished specimens were used to measure the flexural strength with a four-point bending test after storage in water at 37 degrees C for 28 d. Equal procedures and numbers of specimens were used to measure fracture toughness and flexural strength without preloading and storage in water.