Figure 6.

Fractured cantilever beams for all sample groups: nano-fibres and rods were fractured perpendicularly in (a) cantilevers containing nano-fibres and (b) parallelly aligned rods; however, (c) in decussation cantilevers, microcracking (rod boundary cracking) and crack branching along rod boundaries could be observed. In the latter sample group, fracture almost completely occurred within rod boundaries. This and crack deflection along (b) rod interfaces prove that the weak protein-rich interface between rods is the preferential crack path within enamel.