1Department of Mechanical Engineering, Union College, 2Department of Anthropology, Ohio State University, 3Department of Anthropology, University of Florida
Thursday Evening, Park Concourse
We previously reported (AJPA 138:218) that the geometries of cercopithecoid canines convey resistance to a variety of parasagittal loads by analyzing each canine as a tapered straight beam subject to the isostress condition (i.e., each canine maximally stressed to same degree at each section). Herein, we extend that analysis by considering the effects of curvature of the posterior aspect of each canine. If posterior radii of curvature are of the same magnitude as the anteroposterior dimension of the cross section, then accurate assessments of stress require a curved beam analysis.
We determined posterior radii of a sample of 15 permanent maxillary canines from males and females representing 8West African cercopithecoid species. We acquired coordinates along the posterior aspect from the tooth base (i.e., enamel-dentin junction) to the tip with an approximate spacing of 0.5 mm between points using a digitizer. Bezier curves were fit through the data, and radii were determined from the fits using numerical differentiation and the calculus curvature formula.
We found radii of curvature to vary dramatically along the length of individual canines, often by an order of magnitude. The radii are of the same magnitude as the anteroposterior dimension of each cross section at nearly every location along each tooth. At the base, however, where parasagittal bending moments are greatest, radii were up to an order of magnitude less than the anteroposterior dimension. Curved beam effects must be present in anthropoid canines; failure to consider curvature will result in an overestimation of canine bending strength.
Supported by National Science Foundation BCS-922429, BCS-60017683, BCS-0921770, BCS-0922414 and DUE-0511287.