Structure-mechanical function relations at nano-scale in heat-affected human dental tissue.
The knowledge of the mechanical properties of dental materials related to their hierarchical structure is essential for understanding and predicting the effect of microstructural alterations on the performance of dental tissues in the context of forensic and archaeological investigation as well as laser irradiation treatment of caries. So far, few studies have focused on the nano-scale structure-mechanical function relations of human teeth altered by chemical or thermal treatment. The response of dental tissues to thermal treatment is thought to be strongly affected by the mineral crystallite size, their spatial arrangement and preferred orientation. In this study, synchrotron-based small and wide angle X-ray scattering (SAXS/WAXS) techniques were used to investigate the micro-structural alterations (mean crystalline thickness, crystal perfection and degree of alignment) of heat-affected dentine and enamel in human dental teeth. Additionally, nanoindentation mapping was applied to detect the spatial and temperature-dependent nano-mechanical properties variation. The SAXS/WAXS results revealed that the mean crystalline thickness distribution in dentine was more uniform compared with that in enamel. Although in general the mean crystalline thickness increased both in dentine and enamel as the temperature increased, the local structural variations gradually reduced. Meanwhile, the hardness and reduced modulus in enamel decreased as the temperature increased, while for dentine, the tendency reversed at high temperature. The analysis of the correlation between the ultrastructure and mechanical properties coupled with the effect of temperature demonstrates the effect of mean thickness and orientation on the local variation of mechanical property. This structural-mechanical property alteration is likely to be due to changes of HAp crystallites, thus dentine and enamel exhibit different responses at different temperatures. Our results enable an improved understanding of the mechanical properties correlation in hierarchical biological materials, and human dental tissue in particular.
Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United Kingdom. Electronic address: tan.sui@eng.ox.ac.uk.
Tan
T
Sui
School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, United Kingdom.
Michael A
MA
Sandholzer
Institut P',CNRS UPR 3346, University of Poitiers, SP2MI, BP 30179, F86962 Futuroscope Chasseneuil Cedex, France.
Eric
E
Le Bourhis
Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United Kingdom.
Nikolaos
N
Baimpas
School of Dentistry, College of Medical and Dental Sciences, University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, United Kingdom.
Gabriel
G
Landini
Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United Kingdom.
Alexander M
AM
Korsunsky
D001696:Biomechanical Phenomena; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D055595:Mechanical Phenomena; D008963:Molar / Q000166:cytology*; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
Dental tissue; Mechanical-structural correlation; Nanoindentation; SAXS/WAXS; Thermal treatment