title: Magnesium-Assisted Continuous Growth of Strongly Iron-Enriched Incisors.
abstract: Teeth are an excellent example where optimally designed nanoarchitectures with precisely constructed components consist of simple compounds. Typically, these simple constituent phases with insignificant properties show mechanical property amplifications when formed into composite architectures. Material properties of functional composites are generally regulated on the nanoscale, which makes their characterization particularly demanding. Using advanced analytical and imaging transmission electron microscopy techniques, we identified innovative microstructural adjustments combined with astonishing compositional adaptations in incisors of coypu. Unique constituents, recognized as an additional amorphous Fe-rich surface layer followed by a transition zone covering pigmented enamel, provide the required structural stability to withstand repeated mechanical load. The chemically diverse Fe-rich surface layer, including ferrihydrite and iron-calcium phosphates, gives the typical orange-brown coloration to the incisors. Within the spaces between elongated hydroxyapatite crystals in the pigmented enamel, only ferrihydrite was found, implying that enamel pigmentation is a very strictly controlled process. Most significantly, an unprecedentedly high amount of Mg was measured in the amorphous flake-like material within the dentinal tubules of the incisors, suggesting the presence of a (Mg,Ca) phosphate phase. This unusually high influx of Mg into the dentin of incisors, but not molars, suggests a substantial functionality of Mg in the initial formation stages and constant growth of incisors. The present results emphasize the strong mutual correlation among the microstructure, chemical composition, and mechanical properties of mineralized dental tissues.
authors.affiliation: Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart 70569, Germany.
authors.forename: Vesna
authors.identifier: 0000-0001-8864-0931
authors.initials: V
authors.lastname: Srot
authors.affiliation: Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart 70569, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Bussmann
authors.affiliation: Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart 70569, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Salzberger
authors.affiliation: Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart 70569, Germany.|Materials Physics Group, University of Stuttgart , Stuttgart 70569, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Deuschle
authors.affiliation: Department of Materials Science and Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States.
authors.forename: Masashi
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Environmental Protection College , Velenje 3320, Slovenia.|ERICo Velenje, Ecological Research and Industrial Cooperation , Velenje 3320, Slovenia.
authors.forename: Boštjan
authors.initials: B
authors.lastname: Pokorny
authors.affiliation: ERICo Velenje, Ecological Research and Industrial Cooperation , Velenje 3320, Slovenia.
authors.forename: Ida
authors.initials: I
authors.lastname: Jelenko Turinek
authors.affiliation: Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart 70569, Germany.
authors.forename: Alison F
authors.initials: AF
authors.lastname: Mark
authors.affiliation: Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Stuttgart 70569, Germany.
authors.forename: Peter A
authors.initials: PA
authors.lastname: van Aken
keywords: Fe-rich teeth; Mg-enriched dentin; analytical TEM; biomineralization; mechanical properties