Anisotropy of the mechanical properties of human dentin under shear testing

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 similar to 0.6 GPa, the shear strength similar to 65 MPa and the total deformation similar to 30%, whereas the shear strength similar to 40 MPa and total deformation similar to 17% is less for second group but its shear modulus similar to 0.6 GPa 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 similar to 17%, whereas after that anisotropy of the mechanical properties should be taken into account. (C) 2014 Elsevier B.V. All rights reserved.