Nanostructural Analysis of Human Dentine using 3D Small Angle X-ray Scattering Tensor Tomography

Session

Stream 4: Diamond Light Source Session 2

Authors

Tayyaba Rabnawaz (2, 3), Nathanael Leung (2), Robert Harper (4), Tim Snow (3), Leonard Nielsen (1), Richard Shelton (4), Gabriel Landini (4), Andy Smith (3), Nick Terrill (3), Marianne Liebi (1), Tan Sui (2)

Affiliations

1. Department of Applied Physics, Chalmers University of Technology
2. Department of Mechanical Engineering Sciences, University of Surrey
3. Diamond Light Source, Harwell Science and Innovation Campus
4. School of Dentistry, College of Medical and Dental Sciences, University of Birmingham

Keywords

small angle X-ray scattering tensor tomography; nanostructure; human dental tissue; dental caries; artificial demineralisation

Abstract text

Objectives 

Dental caries is one of the most prevalent and costly health issues affecting modern life, which results in the demineralisation and destruction of the dental hard tissues. Demineralisation is a localised process, whereupon the nano-hydroxyapatite (HAp) crystallites in dentine may be dissolved by acid produced by bacteria in dental plaque. This influence both the micro- and nano-structure and its mechanical properties of the affected dental hard tissues. In order to understand the alterations in mechanical properties of naturally and artificially demineralised dental tissue, it is essential to comprehend the correlation between its nanostructural arrangement and the organic and inorganic components.

To investigate the complex structure of dentine at the nano-scale, a recently developed advanced imaging technique called 3D small angle X-ray scattering tensor tomography (3D-SASTT) has been developed and at Beamline I22, Diamond Light Source. This technique was applied to understand the structural variations, of the collagen fibrils and HAp crystallites in dentine occurring in dental caries and artificial demineralisation.

Methods/Materials 

Five dentine sample groups were studied in the 3D-SASTT experimental setup, using two translation axes (x and y) with different rotational angles α (0^o - 180^o) and tilt angles β (0^o - 45^o). Each sample was raster scanned in the x-y planes to cover the field of view using a 14 keV X-ray beam. After collecting the 3D-SASTT dataset, a reconstruction algorithm was used to reveal the 3D structural alterations and changes in orientation of the nano-collagen fibrils and nano-HAp crystallites. 

Results 

The reconstruction revealed the intensity distribution and orientation of collagen fibrils and HAp crystallites. Both natural carious dentine and artificially demineralised dentine showed structural changes with respect to the normal dentine: carious dentine showed more pronounced orientational changes in the nano-collagen fibrils and nano-HAp crystallites compared with the artificially demineralised dentine.

Conclusion

The data indicated that the recently developed 3D-SASTT method was able to detect the 3D structural arrangement of the main dentine components. It was also able to show structural variations in dentine, due to the effect of carious and artificially demineralisation, primarily manifesting themselves as changes in the orientation and degree of orientation of the collagen fibrils and HAp crystallites within the sample studied.

Acknowledgements

Funding from the doctoral studentship from the EPSRC Centre for Doctoral Training in Micro- and Nano Materials and Technologies (EP/L016788/1) at the University of Surrey and Diamond Light Source are gratefully acknowledged and access to the Beamline I22 under the allocation SM20285-1.