The Role of Dust, Grit and Phytoliths in Tooth Wear
Objectives: Particles poising a wear threat to teeth must be both harder than enamel and possess the correct angle of attack. Most natural ‘grit' particles possess sufficient hardness, while effective attack angles may be generated during mastication. Plants produce particles of opaline silica called phytoliths that are embedded in their tissues. These appear not to be hard enough to wear tooth enamel, but evidence suggests they are a form of defense against herbivores. Here the hypothesis that phytoliths mimic grit in the mouths of mammalian herbivores and therefore provide plant protection by deception is investigated.
Methods: Phytoliths were obtained from two grasses Dactylis glomerata and Ampelodesmos mauritanicus, with dust and grit extracted from the Kuwaiti landscape. Particles were subjected to nanoindentation to obtain estimates of hardness (H), elastic modulus (E), and toughness (KIC). Individual dust particles were also subjected to compression tests and their failure strengths calculated.
Results: For grit (n=15): E=94.16±2.29 GPa, H=13.53±0.19 MPa and KIC=0.68±0.08 MPa.m½. For phytoliths: Dactylis glomerata (n=17) E=20.2±1.19 GPa, H=2.76±0.11 MPa and KIC=0.28±0.04 MPa.m½. Ampelodesmos mauritanicus (n=12) E=21.6±2.51 GPa; H = 3.03±0.10 MPa and KIC=0.22±0.05 MPa.m½. Grit particles (n=22) of differing diameters failed at forces of 0.9–150 N, giving a range of failure strengths between 52.6–283.5 GPa.
Conclusions: Grit seems to be the most likely wear agent due to its high hardness. Compression tests prove that they fracture at low forces, rendering fragments with dangerous attack angles. Given that mammals seem capable of detecting particulate fractures in the mouth, it is possible that the fracture of phytoliths during plant consumption resembles that of the natural agents of wear. Therefore, it is suggested that phytoliths could represent an example of mimicry, forming an example of a feeding deterrent operating by deceit.
Acknowledgements: This study was supported by General Facilities Project GE01/07 from Kuwait University.
Van Casteren, Adam
( Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University,, Kuwait, , Kuwait
)
Strait, D.s
( Department of Anthropolgy, Albany, , Albania
)
Atkins, A.g
( Department of Mechanical engineering, London, , England
)
Lucas, Peter
( Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University,, Kuwait, , Kuwait
)
Fadhalah, K
( Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University,, Kuwait, , Kuwait
)
Al-musallam, A
( Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University,, Kuwait, , Kuwait
)
Michael, S
( Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University,, Kuwait, , Kuwait
)
Henry, A.g
( Plant Foods in Hominin Dietary Ecology Group, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany, Leipzig, , Ghana
)
Watzke, J
( Plant Foods in Hominin Dietary Ecology Group, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany, leipzig, , Germany
)
Reed, D.a
( Department of oral biology, chicago, IL, USA
)
Diekwisch, Thomas
( University of Illinois at Chicago, Chicago, IL, USA
)