Localized Deformation of Human Tooth

Mechanical properties of human teeth are key for understanding functions and developing restorative materials, and the distribution of micromechanical properties across the enamel-dentine junction has been rarely explored by micro-scratch tests, especially under clinically-relevant forces. This study aims to explore the localized mechanical responses of the enamel and dentine of a human molar by both nanoindentation and micro-scratch methods. Nanoindentation and micro-scratch tests were carried out on enamel and dentine of a human molar. The mechanical properties (e.g., contact modulus, indentation hardness, wear resistance, plastic deformation resistance, elastic strain capacity, and brittleness index) of enamel and dentine were measured and compared: the enamel exhibits superior mechanical properties (e.g., higher contact modulus, indentation hardness, wear/plastic deformation resistance, and elastic strain capacity) compared to dentine; and dentine has a much smaller brittleness index than enamel. The superior mechanical properties of enamel enable human teeth to maintain bio-functionality in harsh environment, and the smaller brittleness index of dentine allows teeth to absorb mechanical energy from repeated contact/impact without causing structural damages.