Mandibular Biomechanics and Development of the Human Chin

@article{Ichim2006MandibularBA,
  title={Mandibular Biomechanics and Development of the Human Chin},
  author={Ionut P Ichim and M.V. Swain and Julius A. Kieser},
  journal={Journal of Dental Research},
  year={2006},
  volume={85},
  pages={638 - 642}
}
The development of the chin, a feature unique to humans, suggests a close functional linkage between jaw biomechanics and symphyseal architecture. The present study tests the hypothesis that the presence of a chin changes strain patterns in the loaded mandible. Using an anatomically correct 3-D model of a dentate mandible derived from a CT scan image, we analyzed strain patterns during incisal and molar biting. We then constructed a second mandible, without a chin, by ‘defeaturing’ the first… 

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References

SHOWING 1-10 OF 29 REFERENCES

Mandibular stiffness in humans: numerical predictions.

Biomechanics of torsion in the human mandible.

TLDR
Comparative investigations of mandibular function among primates have relied upon elementary structural models to estimate states of masticatory stress and strain, but these models are probably not consistently reliable for predicting the distribution of strains in the corpus.

Comparative Functional Morphology of Maximum Mandibular Opening (Gape) in Primates

There is wide variation among primates in the size and shape of teeth, the size and position of masticatory muscles, and the morphology of the craniofacial skeleton. The functional significance of

Three-dimensional finite element stress analysis of the dentate human mandible.

TLDR
The results suggested that although the mandible behaved in a beam-like manner, its corpus acted more like a combination of open and closed cross sections due to the presence of tooth sockets, at least for the task modelled.

Biomechanical scaling of the hominoid mandibular symphysis

Experimental investigation of mandibular bone strain in cercopithecine primates has established that the mandible is bent in the transverse plane during the power stroke of mastication. Additional

Experimental and finite element study of a human mandible.

TLDR
It is concluded that the applied procedure of generating the FE model is a valid and accurate, non-invasive method to predict different parameters of the complex biomechanical behaviour of human mandibles.

Bone strain following application of a rigid bone plate: an in vitro study in human mandibles.

Stress and strain in the mandibular symphysis of primates: a test of competing hypotheses.

  • W. Hylander
  • Biology
    American journal of physical anthropology
  • 1984
TLDR
The data suggest that during the power stroke of mastication, the macaque symphysis is predominately sheared dorsoventrally and/or twisted about a transverse axis and bent by lateral transverse bending of the mandibular corpora.

Cross-sectional geometry and morphology of the mandibular symphysis in Middle and Late Pleistocene Homo.

TLDR
The decoupling of bending resistance and mentum osseum form in the Late Pleistocene suggests that the evolutionary emergence of the modern human "chin" was at least partly independent of the biomechanical demands placed on the symphysis.