Correction of some mechanical characteristics of human dentin under compression considering the shape effect

The paper is aimed to determine the true compression strength and Poissonʹs ratio of human dentin. The origin of the shape effect in dentin under compression is discussed, too. It was shown that the shape effect is mainly caused by the friction between the surface of the sample and the compression plates. Ratio d/h = 4 is the optimal proportion between the diagonal of compression surface and the height of dentin sample for compression testing. Inhomogeneous deformation takes place in the sample with a low aspect ratio whereas lateral deformation is suppressed in the sample with a high aspect ratio. There is significant difference between the conventional compression strength and the true compression strength. True compression strength of human dentin is 432 ± 16 MPa, the Youngʹs modulus is 4.04 ± 0.12 GPa and Poissonʹs ratio of human dentin is 0.14 ± 0.04.