Structure-mechanical function relations at nano-scale in heat-affected human dental tissue

Area of Science:

• Biomaterials Science
• Nanotechnology
• Dental Research

Background:

• Knowledge of dental material mechanical properties and hierarchical structure is vital for forensic, archaeological, and laser treatment applications.
• Few studies have explored nano-scale structure-mechanical relationships in chemically or thermally altered human teeth.
• Thermal treatment response in dental tissues is influenced by mineral crystallite size, arrangement, and orientation.

Purpose of the Study:

• To investigate micro-structural alterations in heat-affected human dentine and enamel using synchrotron-based X-ray scattering.
• To analyze the spatial and temperature-dependent nano-mechanical properties variation via nanoindentation mapping.
• To correlate ultrastructural changes with mechanical property variations under thermal stress.

Main Methods:

• Utilized synchrotron-based small and wide-angle X-ray scattering (SAXS/WAXS) to assess micro-structural changes (crystalline thickness, perfection, alignment).
• Employed nanoindentation mapping to measure localized nano-mechanical properties (hardness, reduced modulus) as a function of temperature.
• Examined heat-affected dentine and enamel samples from human dental teeth.

Main Results:

• Dentine exhibited a more uniform mean crystalline thickness distribution than enamel.
• Increasing temperature generally increased mean crystalline thickness in both tissues, reducing local structural variations.
• Enamel hardness and reduced modulus decreased with temperature, while dentine showed a reversed trend at high temperatures, linked to hydroxyapatite (HAp) crystallite changes.

Conclusions:

• Dentine and enamel display distinct nano-structural and mechanical responses to thermal treatment due to differences in HAp crystallites and their organization.
• Mean crystalline thickness and orientation significantly influence local mechanical property variations in hierarchical dental tissues.
• Findings enhance understanding of structure-property correlations in biological materials, particularly human dental tissues.