Anisotropy of the mechanical properties of human dentin under shear testing

Abstract

The relationship between of deformation behavior and the orientation of dentin tubules under shear testing is studied. Three orientations of dentin tubules are chosen: (1) dentin tubules lie both parallel to the plane of shift and perpendicular to the direction of loading; (2) they lie both perpendicular to the plane of shift and perpendicular to the direction of loading and (3) the dentin tubules are oriented both parallel to the plane of shift and parallel to the direction of loading. Deformation behavior of the fist and the second groups are the same: the shear modulus ~0.6GPa, the shear strength ~65MPa and the total deformation ~30%, whereas the shear strength ~40MPa and total deformation ~17% is less for second group but its shear modulus ~0.6GPa is the same. Therefore, the direction laid in plane normal to the dentin tubules is easy for fracture. In spite of these differences, human dentin can be considered as an isotropic material at deformation up to ~17%, whereas after that anisotropy of the mechanical properties should be taken into account.