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Stereo photogrammetric characterization of wishboning strain in the colobine mandibular symphysis
Author(s) -
Daegling David John,
Bucinell Ronald,
McGraw William Scott,
Rapoff Andrew Jordan
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.174.4
Subject(s) - symphysis , context (archaeology) , masticatory force , strain (injury) , mandibular symphysis , biomechanics , biology , stress (linguistics) , mandible (arthropod mouthpart) , orthodontics , strain gauge , anatomy , bending , evolutionary biology , structural engineering , medicine , zoology , engineering , paleontology , linguistics , philosophy , genus
The masticatory loading regime of lateral transverse bending (wishboning) is hypothesized to be instrumental in the evolution of symphyseal form among primates. The biomechanics of wishboning have largely been inferred by assuming that the mandible behaves as a curved beam under this load; however, the characterization of stress and strain in the anthropoid symphysis has been interpretively challenging. This is due, in part, to both limitations of sampling strain in an in vivo context and the incongruence of beam theory assumptions on the one hand and the anatomical complexity of mandibular morphology on the other. Utilizing stereo photogrammetry, we employ an in vitro approach to characterize the strain field in a sample of colobine mandibles under simulated wishboning loads in order to assess the utility of idealized curved beam models for characterizing strain gradients in symphyseal bone. This full‐field method also provides an opportunity to evaluate the effects of morphological variation on the distribution of wishboning strains. Conventional theory of curved beams suggest that colobine mandibles should exhibit reduced disparity of labial and lingual stresses relative to papionin primates given differences in overall mandibular architecture. This prediction is borne out by our analysis: whereas macaques experience lingual:labial strain disparities of 3.5:1, the colobine mandibles exhibit ratios on the order of 2‐3:1. Despite the fact that wishboning loads represent a case of asymmetric bending, details of the wishboning strain field do not conform to expected stress distribution under this model.