Functional implications of size reduction in molar dentition during human evolution : using 3D printed models

Camp, Scott T.

April 2019

Thesis or dissertation

© 2019 Scott T Camp. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

During hominin evolution the size of postcanine dentition has varied. While many researchers have tried to make predictions as to the functional significance of these changes, the effect of tooth size on food breakdown has not been quantified.

This thesis develops a novel physical testing rig to compare the fracture performance of teeth of differing sizes on the breakdown of food replicas to examine the relationship between tooth size, food size and breakdown performance. This work presents the design protocol and sensitivity studies carried out in order to develop the methodology for subsequent investigations into dental mechanics.

To examine the effect of dental reduction during human evolution on hard food breakdown stainless steel dental models of a modern Homo sapiens upper and lower dental row were isometrically scaled up. A size series of physical dental rows were attached to a universal testing machine and the efficiency of food breakdown recorded for each (force at initial fracture, energy, displacement and fragmentation), using 3D printed spherical hard brittle food replicas with diameters of 5mm, 10mm, 15mm, and 20mm.

The results of this study suggest that smaller teeth of modern Homo sapiens are slightly more efficient at reducing peak forces and energy consumption of initial fracture of food objects than larger teeth. However, compared to the effect of changes in food size and the location of the bite on the tooth, performance differences between the different tooth sizes were minimal. The results suggest that individuals may be able to access different stress resistant food resources by simply changing how they position a food item, but also suggest that dental reduction during human evolution may have had a minimal impact on the ability of the individual to break hard food items of varying sizes. This study highlights the conflicting constraints placed on teeth and considers the evolutionary, developmental and mechanical mechanisms that may have resulted in the reduced molar size we see during human evolution.

Hull York Medical School, The University of Hull and The University of York
Fitton, Laura C.
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