The aim of this study was to investigate the influence of the test method on fracture toughness of a dental porcelain and a soda lime glass. Three methods were used to determine fracture toughness: the indentation strength (IS) by bending, chevron-notched beam (CNB), and the single-edge-notched beam (SENB). In the IS method, the ratio of elastic modulus to hardness in the formula was determined by two methods: individual measurement for E & H (ISm) as well as direct estimation from Knoop's indentation method (ISk). The tested materials were a dentin porcelain, a traditional feldspar-based leucite-reinforced glass ceramic (Carrara Vincent), and a soda lime glass. Carrara Vincent showed a higher toughness than glass with all three test methods.
