Resumen de Biomechanics of the human mandible including the temporomandibular joint = Biomecánica de la mandíbula humana incluyendo la articulación temporomandibular.
María Soledad Commisso Cuñarro
This thesis is divided into 10 chapters. In chapter 2, the anatomy of the cranium, mandible and joint is described. The relevant anatomical concepts are detailed. Mastication muscles are described together with their insertion and origin areas. The jaw movement during chewing is discussed and related to the muscle activity pattern. This serves as a basis for the loading conditions applied to the finite element model.
In chapter 3, a background of the study is presented. Different tests where the mechanical properties of the articular disc were studied are reviewed. Then a summary of some biomechanical models of the temporomandibular joint found in the literature is carried out. The main results are described. Some dynamic models of the jaw where chewing was simulated by means of forward-dynamics are commented. And finally, a review of the remodeling models proposed to describe the bone density of the mandible is performed.
The biological components of the main tissues included are described in chapter 4. The mechanical properties of bone, articular cartilage and ligaments are related to their composition.
In chapter 5, the bone remodeling model used to describe the anisotropic and time dependent behavior of bone is presented.
In chapter 6, a brief review of Continuum Mechanics is done to introduce the material formulation used to describe the behavior of the disc and ligaments of the joint. Hyperelasticity, transversely isotropy and quasi-linear viscoelasticity (QLV), together with their implementation in a user material subroutine are presented.
In chapters 7 and 8 the mechanical characterization of the articular disc is performed. In chapter 7, an algorithm to fit the experimental curves to the proposed formulation is described and the finite element model used to validate the algorithm and the xperimental setup is shown. In chapter 8, the extraction and conservation protocol of the articular disc is outlined. The sample extraction from the articular disc is described and the initial deformation gradient estimated. The stress relaxation test setup is shown and the set of tests performed is presented. The different tests, at different strain levels and at different strain rates, were fitted with the proposed material model. A statistic analysis was done to prove the validity of the QLV formulation to describe the articular disc behavior. A genetic algorithm (appendix B) was implemented to fit the QLV model to the experimental curves.
Chapter 9 is dedicated to the finite element model of the mandible and temporomandibular joint. The geometry and mesh of every component is described. The contact formulation used to simulate the interaction between the components of the joint is discussed. The muscles activity pattern applied to simulate chewing and clenching is presented and the results obtained are compared with literature.
Finally, chapter 10 summarizes the main conclusions obtained from this thesis and the future work to be done.
