Study of the deformations of the isolated mandible under static constraints by simulation on a physicomathematical model.

The authors have studied the deformations of a mandible isolated from its muscular environment and submitted to statical constraints, with the help of a "modified model" and the finite elements method: the general deformation of the mandible and its modifications according to the direction of the application of the pressure, the rotation phenomenon or "torsion" in cross sections (identified by computer) of the mandible, the respective deformations of the internal and external corticals have successively been calculated. Particular mechanical phenomenons corresponding to the areas where the anatomo-clinical forms of the mandibular fractures take place have clearly been shown. The authors draw the conclusion that the mandible behaves mechanically in a similar way to a tridimensional composite.

Study of the mandible under static constraints by holographic interferometry. New biomechanical deductions.

In order to try to determine the nature of the mechanical structure of the mandible, the authors have compared, with the help of holographic interferometry, the behavior of the fresh mandible of a corpse, of a representative iron angle, and of a block of carbon-carbon under static constraint. There are no similarities between the behavior of the human mandible and that of a polycrystalline steel. On the contrary, the behavior of the mandible and of the carbon-carbon block are very similar. It would be hasty to state that bones are a heterogeneous composite. We can only prove, in a first approach, that they behave similarly under identical experimental conditions. The authors also demonstrated that the mandible presents a "mechanical hysteresis" phenomenon. This means that, when subjected to a small strain, its shape changes, but this change tends to neutralize itself in part in the course of time.