The hidden structure of human enamel
Author(s)Jung, Gang Seob; Qin, Zhao; Buehler, Markus J.
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Enamel is the hardest and most resilient tissue in the human body. Enamel includes morphologically aligned, parallel, ∼50 nm wide, microns-long nanocrystals, bundled either into 5-μm-wide rods or their space-filling interrod. The orientation of enamel crystals, however, is poorly understood. Here we show that the crystalline c-axes are homogenously oriented in interrod crystals across most of the enamel layer thickness. Within each rod crystals are not co-oriented with one another or with the long axis of the rod, as previously assumed: the c-axes of adjacent nanocrystals are most frequently mis-oriented by 1°–30°, and this orientation within each rod gradually changes, with an overall angle spread that is never zero, but varies between 30°–90° within one rod. Molecular dynamics simulations demonstrate that the observed mis-orientations of adjacent crystals induce crack deflection. This toughening mechanism contributes to the unique resilience of enamel, which lasts a lifetime under extreme physical and chemical challenges.
DepartmentMassachusetts Institute of Technology. Department of Civil and Environmental Engineering; Massachusetts Institute of Technology. Laboratory for Atomistic and Molecular Mechanics
Springer Science and Business Media LLC
Beniash, Elia et al. "The hidden structure of human enamel." Nature communications 10 (2019): 1038 © 2019 The Author(s)
Final published version
General Biochemistry, Genetics and Molecular Biology, General Physics and Astronomy, General Chemistry