Alistair R. Evans1,2
and
Gordon D. Sanson1
1School of Biological Sciences, Monash University,
Victoria 3800,
Australia
2Current address: Institute of Biotechnology, PO Box
56 (Viikinkaari 9), FIN-00014 University of
Helsinki, Finland
This page contains the three-dimensional models of tooth forms constructed in Evans and Sanson (2006) Journal of Morphology 267 (6): 649-662.
Abstract
The interaction between the two main competing geometric determinants
of
teeth (the geometry of function and the geometry of occlusion) were
investigated
through the construction of three-dimensional spatial models of several
mammalian
tooth forms (carnassial, insectivore premolar, zalambdodont,
dilambdodont
and tribosphenic). These models aim to emulate the shape and function
of
mammalian teeth. The geometric principles of occlusion relating to
single-
and double-crested teeth are reviewed. Function was considered using
engineering
principles that relate tooth shape to function. Substantial similarity
between
the models and mammalian teeth were achieved. Differences between the
two
indicate the influence of tooth strength, geometric relations between
upper
and lower teeth (including the presence of the protocone) and wear on
tooth
morphology. The concept of ‘autocclusion’ is expanded to include any
morphological
features that ensure proper alignment of cusps on the same tooth and
other
teeth in the tooth row. It is concluded that the tooth forms examined
are
auto-aligning, and do not require additional morphological guides for
correct
alignment. The model of therian molars constructed by Crompton and
Sita-Lumsden
(1970; Nature 227: 197-199) is reconstructed in
three-dimensional
space to show that their hypothesis of crest geometry is erroneous, and
that
their model is a special case of a more general class of models.
3-D Models
A VRML browser is required to view the .wrl files on this page. VRML browser plug-ins for Netscape and Internet Explorer: PC (CosmoPlayer or (Cortona VRML Client); Mac (Cortona VRML Client for Mac).
Instructions for how to use CosmoPlayer.
The following conventions are used in the models on this page:
Lower tool: yellow
Upper tool: blue
Lower tool moves upwards to upper tool
following
the occlusal vector (red arrow), and upper tool remains stationary.
Occlusal Geometrical Principles
Single-bladed models
| Simple single-bladed models used as starting points for modeling mammalian teeth, illustrating occlusal geometrical principles. a) symmetrical with vertical movement. Full page |
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| b) symmetrical with latero-vertical movement. Full page |
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| c) asymmetrical with latero-vertical movement. Full page |
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Alistair Evans and Gordon
Sanson,
December 2003