Investigation on the microtribological behaviour of human tooth enamel by nanoscratch

Abstract With a nanoscratch tester, the microtribological behaviour of human tooth enamel was investigated by a spherical diamond tip. Before tests, the molars were longitudinally sectioned, well polished and etched in 0.001 M citric acid solution for 1 min. The experimental results indicated that the scratching behaviour of enamel was closely associated with its microstructure. Due to the “buffer” effect of the inter-rod enamel, the scratch-induced damage along the parallel direction to the enamel rod axis was weaker than that along the vertical direction especially under high loads. Under the same load, the scratch depth on the inter-rod enamel was much larger than that on the enamel rods. When the normal load increased from 0 to 0.5 mN during scratching, the size of enamel hydroxyapatite (HA) particles was found to gradually decrease from 70 nm to 20 nm. Since such behaviour may be helpful to release the stress concentration and prevent the propagation of micro cracks in teeth during the masticating process, it can effectively improve the wear property of teeth. Finally, after the scratched sample was remineralized in the artificial saliva solution, the size of particles on the surface was found to increase to 200 nm and the scratching damage could be repaired to some extent. The results may provide useful suggestions on the development of dental restorative materials and biomimetic materials.