title: A mineralogical study in contrasts: highly mineralized whale rostrum and human enamel.
abstract: The outermost enamel of the human tooth and the rostrum of the whale Mesoplodon densirostris are two highly mineralized tissues that contain over 95 wt.% mineral, i.e., bioapatite. However, the same mineral type (carbonated hydroxylapatite) does not yield the same material properties, as revealed by Raman spectroscopy, scanning electron microscopy, electron microprobe analysis, and synchrotron X-ray diffraction analysis. Overall, the outermost enamel of a tooth has more homogeneous physical and chemical features than the rostrum. Chemical comparison of rostrum and enamel shows bioapatite in the rostrum to be enriched in Na, Mg, CO3, and S, whereas the outermost enamel shows only a slightly enriched Cl concentration. Morphologically, mineral rods (at tens of μm scale), crystallites and prisms (at μm and sub-μm scale), and platelets (at tens of nm scale) all demonstrate less organized texture in the rostrum than in enamel. Such contrasts between two mineralized tissues suggest distinct pathways of biomineralization, e.g., the nature of the equilibrium between mineral and body fluid. This study illustrates the remarkable flexibility of the apatite mineral structure to match its chemical and physical properties to specific biological needs within the same animal or between species.
authors.affiliation: Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, 63130, USA.|College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.affiliation: Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 4NS, UK.
authors.forename: Maisoon
authors.initials: M
authors.lastname: AI-Jawad
authors.affiliation: Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 4NS, UK.
authors.forename: Samera
authors.initials: S
authors.lastname: Siddiqui
authors.affiliation: Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, 63130, USA.
authors.forename: Jill D
authors.initials: JD
authors.lastname: Pasteris
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic; D003743:Dental Enamel / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D013059:Spectrum Analysis, Raman; D014070:Tooth / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D014907:Whales; D014961:X-Ray Diffraction