Influence of the geometry of ceramic specimens on biaxial flexural strength: experimental testing and finite element analysis

Abstract

Abstract This study evaluated the influence of the geometry of ceramic specimens (disc vs. square plate) on the biaxial flexural strength (BFS) using an experimental set and finite element analysis (FEA). Leucite glass-ceramic blocks were used in the preparation of disc (D; n=14) and square plate (S; n=13) specimens with the same lower (tensile) surface area. The specimens were subjected to a piston-on-three-ball flexural test (ISO 6872:2008). To calculate the BFS of the S group, the specimen radius, indicated by the ISO 6872:2008 formula for discs, was replaced by half of the side length. FEA compared the pattern of stress distribution and the first principal stress between D and S specimens having the same and different lower (tensile) surface area. Student’s t-test showed no difference (p=0.85) in the BFS between D (95.0±9.6 MPa) and S (84.3±10.3 MPa). FEA indicated a similar pattern of stress distribution, with almost no difference in the first principal stress of discs and square plates with the same lower (tensile) surface area. In the experimental condition investigated, square plate ceramic specimens can be used in piston-on-three-ball tests. For the calculation of the BFS, the specimen radius may be replaced by half side length of the square specimen.

Keywords

• biaxial flexural strength
• finite element method
• dental ceramic
• specimen shape