Mammalian tooth enamel functional sophistication demonstrated by combined nanotribology and synchrotron radiation FTIR analyses

Chen-Tzu Chiu; Jyun-Kai Cao; Pei-Wen Wang; Ya-Na Wu; Yao-Chang Lee; Yeau-Ren Jeng; Dar-Bin Shieh; Robert R Reisz

doi:10.1016/j.isci.2022.105679

Mammalian tooth enamel functional sophistication demonstrated by combined nanotribology and synchrotron radiation FTIR analyses

iScience. 2022 Dec 27;26(1):105679. doi: 10.1016/j.isci.2022.105679. eCollection 2023 Jan 20.

Authors

Chen-Tzu Chiu¹, Jyun-Kai Cao², Pei-Wen Wang^{1

3}, Ya-Na Wu^{1

4}, Yao-Chang Lee^{5

6

7}, Yeau-Ren Jeng^{2

8

9

10}, Dar-Bin Shieh^{1

3

4

11}, Robert R Reisz^{12

13}

Affiliations

¹ School of Dentistry and Institute of Oral Medicine, National Cheng Kung University, Tainan 701401, Taiwan.
² Department of Mechanical Engineering, National Chung Cheng University, Chia-Yi 62100, Taiwan.
³ Center of Applied Nanomedicine and Core Facility Center, National Cheng Kung University, Tainan 701401, Taiwan.
⁴ iMANI Center of the National Core Facility for Biopharmaceuticals, National Science and Technology Concil, Taipei 106214, Taiwan.
⁵ Life Science Group, National Synchrotron Radiation Center, Hsinchu 30076, Taiwan.
⁶ Department of Optics and Photonics, National Central University, Chung-Li 32001, Taiwan.
⁷ Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
⁸ Department of Biomedical Engineering, National Cheng Kung University, Tainan 70101, Taiwan.
⁹ Medical Device Innovation Center, National Cheng Kung University, Tainan 70101, Taiwan.
¹⁰ Academy of Innovative Semiconductor and Sustainable Manufacturing, National Cheng Kung University, Tainan 70101, Taiwan.
¹¹ Department of Stomatology, National Cheng Kung University Hospital, Tainan 704302, Taiwan.
¹² International Centre of Future Science, Dinosaur Evolution Research Center, Jilin University, Changchun, Jilin 130012, China.
¹³ Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada.

Abstract

The teeth of limbed vertebrates used for capturing and processing food are composed of mineralized dentine covered by hypermineralized enamel, the hardest material organisms produce. Here, we combine scanning probe microscopy, depth sensing, and spectromicroscopy (SR-FTIR) to characterize the surface ultrastructural topography, nanotribology, and chemical compositions of mammal species with different 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. It provides the ability to dissipate stress under loading and prevent mechanical failure. Evolutionary change in the biochemical composition and biomechanical properties of mammalian dentition is related to variations in the oral processing of different food materials.

Keywords: Biomaterials; Evolutionary biology; Materials chemistry; Materials science; Materials structure.