To identify the crystallographic unit cell of human dental enamel

Abstract The inorganic matter in human tooth enamel (HTE) is related to the hexagonal unit cell of hydroxyapatite (HAP), but carbon, magnesium, and sodium are also detected by Energy-Dispersive X-ray spectroscopy (EDS) in addition to HAP’s elements. These elements are attributed to ionic substitutions within the HAP unit cell, where Ca 2+ ions are partially replaced by Mg 2+ and Na + ions, and the PO 4 3− and OH − ions are partially replaced by carbonate (CO 3 2− ) ions. Simulations of HAP-related structures have indicated that these substitutions induce a slight distortion, transforming the unit cell from hexagonal to triclinic. Therefore, with the aim of recovering the hexagonal system for HTE, a $$\sqrt{3}\times \sqrt{3}\times 1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mn>3</mml:mn> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mn>3</mml:mn> </mml:msqrt> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> hexagonal supercell based on the HAP unit cell including the additional CO 3 2− , Mg 2+ and Na + ions was generated. However, the crystallographic elements observed in the convergent beam electron diffraction (CBED) patterns indicate that the system remains triclinic. Graphic Abstract