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X-ray Linear Dichroism in Apatite

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  • Cayla A. Stifler, University of Wisconsin-Madison
  • ,
  • Nina Kølln Wittig
  • Michel Sassi, Pacific Northwest National Laboratory
  • ,
  • Chang Yu Sun, University of Wisconsin-Madison
  • ,
  • Matthew A. Marcus, Lawrence Berkeley National Laboratory
  • ,
  • Henrik Birkedal
  • Elia Beniash, School of Dental Medicine
  • ,
  • Kevin M. Rosso, Pacific Northwest National Laboratory
  • ,
  • Pupa U.P.A. Gilbert, University of Wisconsin-Madison

The recent observation in parrotfish teeth of X-ray linear dichroism motivated an in-depth investigation into this spectroscopic effect in various apatite crystals, including geologic hydroxyapatite (Ca5(PO4)3OH), fluorapatite (Ca5(PO4)3F), and their biogenic counterparts in human bone, mouse enamel, and in parrotfish bone, dentin, and enameloid, the equivalent of dental enamel in certain fish. These data are important because they now enable visualization of the nano- to microscale structure of apatite crystals in teeth and bone. Polarization-dependent imaging contrast (PIC) maps of lamellar bone, obtained with a new method that minimizes space-charge and charging effects, show the expected rotating apatite crystal orientations. PIC maps of mouse enamel reveal a complex arrangement of hydroxyapatite crystals perpendicular to the dentin-enamel junction, with rods arranged in a decussation pattern in inner enamel and nearly parallel to one another in outer enamel. In both inner and outer enamel crystal c-axes are not always aligned with the rod elongation direction.

Original languageEnglish
JournalJournal of the American Chemical Society
Pages (from-to)11698-11704
Number of pages6
Publication statusPublished - 1 Sept 2018

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