title: Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation.
abstract: The giant panda׳s teeth possess remarkable load-bearing capacity and damage resistance for masticating bamboos. In this study, the hierarchical structure and mechanical behavior of the giant panda׳s tooth enamel were investigated under indentation. The effects of loading orientation and location on mechanical properties of the enamel were clarified and the evolution of damage in the enamel under increasing load evaluated. The nature of the damage, both at and beneath the indentation surfaces, and the underlying toughening mechanisms were explored. Indentation cracks invariably were seen to propagate along the internal interfaces, specifically the sheaths between enamel rods, and multiple extrinsic toughening mechanisms, e.g., crack deflection/twisting and uncracked-ligament bridging, were active to shield the tips of cracks from the applied stress. The giant panda׳s tooth enamel is analogous to human enamel in its mechanical properties, yet it has superior hardness and Young׳s modulus but inferior toughness as compared to the bamboo that pandas primarily feed on, highlighting the critical roles of the integration of underlying tissues in the entire tooth and the highly hydrated state of bamboo foods. Our objective is that this study can aid the understanding of the structure-mechanical property relations in the tooth enamel of mammals and further provide some insight on the food habits of the giant pandas.
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
authors: Z Y
authors: ZY
authors: Weng
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA. Electronic address: zqliu@berkeley.edu.
authors: Z Q
authors: ZQ
authors: Liu
authors: Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA.
authors: R O
authors: RO
authors: Ritchie
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
authors: D
authors: D
authors: Jiao
authors: China Conservation & Research Centre for the Giant Panda, Wolong 623003, China.
authors: D S
authors: DS
authors: Li
authors: China Conservation & Research Centre for the Giant Panda, Wolong 623003, China.
authors: H L
authors: HL
authors: Wu
authors: China Conservation & Research Centre for the Giant Panda, Wolong 623003, China.
authors: L H
authors: LH
authors: Deng
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: zhfzhang@imr.ac.cn.
authors: Z F
authors: ZF
authors: Zhang
mesh_terms: D000818:Animals; D003743:Dental Enamel; D006244:Hardness; D013314:Stress, Mechanical; D014070:Tooth; D001503:Ursidae; D016474:Weight-Bearing
keywords: Anisotropy; Giant panda; Hierarchical structure; Indentation; Tooth enamel; Toughening mechanisms