Mammalian Tooth Enamel Functional Sophistication Demonstrated by Combined Nanotribology and Synchrotron Radiation FTIR Analyses

Abstract

The teeth of limbed vertebrates used for capturing and processing food are composed of mineralized dentine covered by hypermineralized enamel, the hardest material produced by organisms. Here we combine scanning probe microscopy, depth-sensing, and spectro-microscopy (SR-FTIR) to characterize the surface ultrastructural topography, nanotribology, and chemical compositions of mammal species with various dietary habits, including omnivorous humans. Our synergistic approach shows that enamel with greater surface hardness or thickness exhibited a more salient gradient feature from the tooth surface to the Dentino-Enamel Junction (DEJ) one that corresponds to the in-situ phosphate-to-amide ratio. This gradient feature of enamel covering softer dentine is the determining factor of the amazingly robust physical property of this unique biomaterial and provides the ability to dissipate stress under loading and prevent mechanical failure. Evolutionary change in the biochemical composition and biomechanical property of mammalian dentition is related to variation in oral processing of different food materials.

Keywords: Mammalian tooth Enamel, Nanotribology, SR-FTIR, Evolution of enamel characteristics in mammals