Bio-inspired design of dental multilayers: experiments and model.

This paper combines experiments, simulations and analytical modeling that are inspired by the stress reductions associated with the functionally graded structures of the dentin-enamel-junctions (DEJs) in natural teeth. Unlike conventional crown structures in which ceramic crowns are bonded to the bottom layer with an adhesive layer, real teeth do not have a distinct "adhesive layer" between the enamel and the dentin layers. Instead, there is a graded transition from enamel to dentin within a approximately 10 to 100 microm thick regime that is called the Dentin Enamel Junction (DEJ). In this paper, a micro-scale, bio-inspired functionally graded structure is used to bond the top ceramic layer (zirconia) to a dentin-like ceramic-filled polymer substrate. The bio-inspired functionally graded material (FGM) is shown to exhibit higher critical loads over a wide range of loading rates. The measured critical loads are predicted using a rate dependent slow crack growth (RDEASCG) model. The implications of the results are then discussed for the design of bio-inspired dental multilayers.