Comparison of fracture toughness measurements for zirconia materials using two test methods

To determine the influence of the fracture toughness (K-IC) methods [single-edge-V-notch-beam (SEVNB) and chevron-notch-beam (CNB)] as well as an optional heat treatment on the K-IC of three different zirconia generations (1st: ZI, 3rd: FX, 4th: HT). One hundred and twenty specimens each (3x4x45 mm) were fabricated, sintered, notched (n=360) and half of them heat treated before K-IC measurements with 4-point-flexural-strength test. SEM images of the notches were recorded. Highest K-IC was found for ZI followed by HT and FX. SEVNB resulted in significantly higher K-IC than CNB. Heat treatment resulted in decrease for SEVNB and increase for CNB of K-IC (except for FX). Groups tested using CNB showed higher reliability of values (Weibull modulus) than tested using SEVNB. SEM images present crack path and fracture surface. Different zirconia materials lead to different K-IC values. The test method and a prior heat treatment showed an influence on the K-IC values and their reliability.