Evolution of the Material Properties of Mineralized Dental Tissues
During their 473 million-year diversification, gnathostomes came to exploit an unprecedented variety of trophic niches. Modifications to dental form and mineralized tissue constituents (i.e. enamel, dentines and in a few taxa, cementum) facilitated their exploitation of novel prey...
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| Format: | Others |
| Language: | English English |
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Florida State University
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| Online Access: | http://purl.flvc.org/fsu/fd/FSU_FALL2017_Kay_fsu_0071N_14152 |
| Summary: | During their 473 million-year diversification, gnathostomes came to exploit an unprecedented variety of trophic niches. Modifications
to dental form and mineralized tissue constituents (i.e. enamel, dentines and in a few taxa, cementum) facilitated their exploitation of
novel prey and/or plant matter. In general, it has been assumed that the intra-tissue level biomechanics of these constituents had little
bearing on whole-tooth functionality, aside from enamel in mammals showing dental occlusion. Specifically, many mammals possess teeth that
self-wear to functionality and show a diversity of derived dental tissues (e.g. prismatic enamel fabrics, coronal cementum) – some which have
been shown to possess unique biomechanical attributes to resist wear and fracture. Here I formally test the hypothesis that the primitive
gnathostome hard tissue material properties remained static prior to the cladogenesis of Mammalia. An ancillary goal is to glean initial
insights on how the material properties of these dental tissues in non-mammalian and mammalian taxa may contribute to whole-tooth form,
function, performance and diets. Properties were tested and examined using two standardized material science techniques, microindentation and
nanoindentation, as well as a novel technique for quantifying fracture propagation from cracks formed during microindentation. The results
from this investigation suggest these material properties are highly variable among gnathostome dentitions. Aside from hardness, there is not
a significant relationship between most material properties and diet aside from enamel hardness. There are also complex fracture patterns
seen in the enamels of mammals and chondrichthyans, showing that gnathostome lineages independently evolved properties to control fracture
and damage done to tooth enamel. Overall, this study suggests that in the case of enamel hardness, natural selection operated at the tissue
level to bring about shifts in tooth functionality throughout the gnathostome radiation. More material properties (i.e. fracture toughness)
need to be investigated to uncover the true functional import of material properties in dental tissues and establish how the tissue complexes
contributed to whole tooth function. === A Thesis submitted to the Department of Biological Science in partial fulfillment of the requirements for
the degree of Master of Science. === Summer Semester 2017. === August 1, 2017. === biomaterials, material properties, nanoindentation, teeth === Includes bibliographical references. === Gregory M. Erickson, Professor Directing Thesis; Steven Lenhert, Committee Member; William S. Oates,
Committee Member; Scott J. Steppan, Committee Member. |
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