Calculation of anisotropic properties of dental enamel from synchrotron data

Abstract

Obtaining information about the intrinsic structure of polycrystalline materials is of prime importance owing to the anisotropic behaviour of individual crystallites. Grain orientation and its statistical distribution, i.e. the texture, have an important influence on the material properties. Crystallographic orientations play an important role in all kinds of polycrystalline materials such as metallic, geological and biological. Using synchrotron diffraction techniques the texture can be measured with high local and angular resolving power. Here methods are presented which allow the spatial orientation of the crystallites to be determined and information about the anisotropy of mechanical properties, such as elastic modulus or thermal expansion, to obtained. The methods are adapted to all crystal and several sample symmetries as well as to different phases, for example with overlapping diffraction peaks. To demonstrate the abilities of the methods, human dental enamel has been chosen, showing even overlapping diffraction peaks. Likewise it is of special interest to learn more about the orientation and anisotropic properties of dental enamel, since only basic information is available up to now. The texture of enamel has been found to be a tilted fibre texture of high strength (up to 12.5×). The calculated elastic modulus is up to 155 GPa and the thermal expansion up to 22.3 × 10(-6)°C(-1).

Ultrastructural evaluation of enamel after dental bleaching associated with fluoride

“…Nanoindentation test is an emerging technique for mechanical property evaluation. With the development of thin‐film materials (Nix,1997) and an increased interest in the surface properties of materials, nanoindentation test has increasing partially, because microhardness testing has frequently proven to be inadequate for the small scales that are important in these fields, and human enamel is an anisotropic composite, consisting of aligned prism rods with protein‐rich sheath (Raue and Klein,2011).…”

New insights in prism orientation within human enamel

“…The lower values in the other measured positions represent a lower demand of strength in that position. Combining the information about the degree of orientation with the spatial orientation of the maximum values and the type of orientation (tilted fibre texture: Raue,2008;Raue and Klein,2010;Raue and Klein 2011), one can deduce the orientation of the enamel prisms (since the HA crystallites link up along their c-axis, Poole and Brooks,1961), the inner building structure of the prisms and one can also justify the orientation of the prisms with the mechanical needs which have to be fulfilled. Looking at point A to F in the molar (cf.…”

A timeline of biological assessments: Our nonspatial continuum

“…Something to consider, Dr. Nakabayashi reported that the general breaking (cohesive) capacity of normal human dentine is approximately 21-megapascals (MPa) [90,91] . On the other hand, the calculated modulus of enamel is up to 155 GPa & the thermal expansion is up to 2.3 X 10 [92]. In 1956, Craig & Peyton demonstrated that enamel & dentine have regional density extremes, which they demonstrated by Knoop indentation tests [93].…”