Exceptional mechanical performance of dental enamel in the harsh environment of oral
cavity can be preserved on decade timescale, which is a unique property in comparison
with functional nanomaterials. Hierarchic architecture of enamel, based on site-specific
structural organization of apatite nanocrystals has a key role in this durability.
In the present study, a novel SEM imaging based method is presented for obtaining
quantitative information on enamel prism orientation in sound primary dental enamel.
This missing puzzle of quantification of the hierarchical enamel structure, along
with spatial mechanical and chemical mapping, shed light on the optimum anisotropic
gradient behaviour of elastic modulus of dental enamel. Specifically, orientation
and composition dependent contributions in both the spatially changing hardness and
elastic modulus were separated. Anisotropy of the enamel’s modulus was predicted and
verified by the spatial variation of average prism orientation. Based on our results
we conclude that the anisotropy of modulus for the bulk enamel arises from the elastic
gradient in direction normal to the enamel external surface combined with the nearly
constant value of modulus in the perpendicular cross section. This behaviour results
in high surface strength and additionally can be responsible to the superior durability
of human enamel.
