Nanoindentation of Teeth: A Hard but Tough Hybrid Functionally Graded Composite

Tooth microstructure is an important factor in determining resilience against damage accumulation. It has specialized hierarchical structure starting from the smallest level to its final macrostructure. Nanoindentation techniques are used to map profiles of elastic modulus and hardness across sections from the dentine-enamel junction to the outer tooth surface. The microstructural hierarchy and precise distribution of organic components endow dental hard tissues with excellent anisotropic mechanical properties, which ensure their lifetime survival in mouth as a load bearing organ. This chapter reviews the application of nanoindentation technique to dental hard tissue studies and discusses the relevant implications in respect to the microstructural and compositional characteristics of these natural biocomposites. It reviews the nanoindentation studies on enamel and dentine. As enamel is the outmost layer of tooth, its mechanical properties are more important and significant for developing restorative materials. The mechanical property of enamel includes mainly elasticity, hardness, visco-elasticity, and fracture behavior. The chapter discusses the elastic property and hardness.