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 (E/H) in the formula was determined by two methods: individual measurement for E and 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 (P < 0.01) than glass with all three test methods. The toughness values manifested significant differences between the methods used (P < 0.01). The two-way analysis of variance suggested that the materials tested and the test methods used had interaction effects, which statistically means that differences in materials and methods influenced the comparability of the toughness result. In this study, a first step was made to compare different toughness test methods by testing the toughness of a traditional feldspar-based leucite-reinforced glass ceramic and a soda lime glass that has a homogeneous microstructure. An interaction effect of the method and the material used was shown. As a consequence, none of the methods tested is suitable as a universal fracture toughness test method. Further research is needed to investigate more extensively the influence of material composition on the fracture toughness test methods' comparability.