Zinc mobility and chemical stability in the biogenic tooth nanocomposite of dentine

Zinc is a natural trace-element in the natural biocomposite dentine that makes up the bony part of teeth. It can additionally diffuse out of artificially placed filling materials, as occasionally reported for clinically-used Zn containing biomaterials (e.g. root canal gutta-percha). Diffusion is extensive with high concentrations that can percolate many hundreds of µm across the bulk of the tooth, as we recently showed. This diffusion causes changes in the micro-structure and chemistry of dentine which have to be understood to determine benefits or possible slow degradation to healthy dentine. Filling materials typically contain ZnO while natural Zn can either be incorporated in the apatite crystals or reside in MMPs in the organic component, which we investigate by XANES. We propose to map the chemical state of Zn to elucidate relationships between resident and diffusion species in healthy dentine near filling material.