Method: Tooth cross-sections (500µm thickness) were prepared from freshly extracted posterior teeth prior to the small-angle X-ray scattering experiment at the I22 beamline (Diamond Light Source Synchrotron Facility, Oxford, UK). A focused (14.5×19µm) monochromatic x-ray beam at a photon energy of 18keV was used to collect 1400 scattering patterns in transmission mode from fixed locations within the sample, and quantitative SAXS analysis was done using established methods.
Result: A mean crystalline thickness of 1.94±0.06nm in dentine and 3.81±0.28nm in enamel was found, with decreasing trends towards the dentine-enamel junction (DEJ). Overall, the crystals appeared needle-shaped and less orientated in dentine compared with a high degree of aligned, plate-like shaped crystals in enamel. A higher degree of alignment was present in dentine near the DEJ, representing an internal nanostructural adaption to optimize the mechanical performance of the softer dentine at the interface with the harder enamel.
Conclusion: There are local structural differences in crystalline size, shape and alignment which demonstrate an internal nano- and micro-structural adaptation in response to specific mechanical requirements of dental tissues. This morphological and structural composition of natural teeth could inspire the development of specific artificial components to enable nanotechnology-based dental treatments and improve the endurance of dental restorations.