Structure-Function Correlative Microscopy of Peritubular and Intertubular Dentine
T. Sui, Jiˇrí Dluhoš, T. Li, K. Zeng, A. Cernescu, G. Landini and A. M. Korsunsky 6
Materials 11, 1493 (2018)
Peritubular dentine (PTD) and intertubular dentine (ITD) were investigated by 3D
correlative Focused Ion Beam (FIB)-Scanning Electron Microscopy (SEM)-Energy Dispersive
Spectroscopy (EDS) tomography, tapping mode Atomic Force Microscopy (AFM) and scattering-type
Scanning Near-Field Optical Microscopy (s-SNOM) mapping. The brighter appearance of PTD
in 3D SEM-Backscattered-Electron (BSE) imaging mode and the corresponding higher grey value
indicate a greater mineral concentration in PTD (~160) compared to ITD (~152). However, the 3D
FIB-SEM-EDS reconstruction and high resolution, quantitative 2D map of the Ca/P ratio (~1.8) fail
to distinguish between PTD and ITD. This has been further confirmed using nanoscale 2D AFM
map, which clearly visualised biopolymers and hydroxyapatite (HAp) crystallites with larger mean
crystallite size in ITD (32 ±8 nm) than that in PTD (22 ±3 nm). Correlative microscopy reveals that the principal difference between PTD and ITD arises primarily from the nanoscale packing
density of the crystallites bonded together by thin biopolymer, with moderate contribution from
the chemical composition difference. The structural difference results in the mechanical properties
variation that is described by the parabolic stiffness-volume fraction correlation function introduced
here. The obtained results benefit a microstructure-based mechano-chemical model to simulate the
chemical etching process that can occur in human dental caries and some of its treatments.