Nanomechanical properties and microtribological behaviours of human tooth enamel

Abstract

Abstract

Nanomechanical properties and microtribological behaviours of human tooth enamel have been investigated using the nanoindentation and nanoscratch techniques. Nanoscratch tests were conducted along different directions in the occlusal and axial sections of enamel under different normal loads. The results showed that for a single enamel rod, the hardness and Young's modulus were higher in the central head area and tended to be lower in the edge area, especially in the tail area. In the occlusal section, the enamel presented higher wear resistance at low loads owing to the compact alternate arrangement of mineral and organic phases within the enamel and the heterogeneous mechanical properties of enamel rods. No obvious material removal occurred, and the surface lesion of enamel was characterized mainly by plastic deformation. As the load increased, significant material removal occurred as a result of brittle delamination, and the coefficient of friction increased and fluctuated. The wear resistance of the axial section was inferior to that of the occlusal section, and moreover, the enamel demonstrated anisotropic microtribological properties in the axial section. Both the friction coefficient and wear loss were higher when the scratches were conducted along the direction of enamel rods.