Spatial and Functional Modeling of Carnivore and Insectivore Molariform Teeth

Alistair R. Evans1,2 and Gordon D. Sanson1
1School of Biological Sciences, Monash University, Victoria 3800, Australia
Current 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.

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

b) symmetrical with latero-vertical movement. Full page

c) asymmetrical with latero-vertical movement. Full page

Next page

Alistair Evans and Gordon Sanson, December 2003