Measuring fracture toughness of human dental enamel at small scale using notched microcantilever beams

Dental enamel is the most mineralised hard tissue with a complex hierarchically organised anisotropic structure and it protects human teeth from mechanical damage during the dental function. Due to the sample size constraints, the available data for quantitative evaluation of the fracture toughness of human enamel is very limited. Here, on the basis of microstructural characterisation, the fracture toughness of human dental enamel at small scale with respect to orientation was measured using notched microcantilever beams fabricated by focussed ion beam. The fracture toughness of human enamel with perpendicular orientation was measured to be 1.244 ± 0.12 MPa · m^1/2, 80% tougher than that of in-plane parallel orientation (0.698 ± 0.18 MPa · m^1/2). The present results are expected to provide deep insights into cusp fractures and the synthesis of enamel-like restorative materials.