Comparison of stress distribution in the temporomandibular joint during jaw closing before and after symphyseal distraction: a finite element study.

The aim of this study was to predict stress modification in the temporomandibular joint (TMJ) after symphyseal distraction (SD). The study was performed using three-dimensional finite element analysis using a complete mastication model. Geometric data were obtained from MRI and CT scans of a healthy male patient and each component was meshed as various regions. The distraction was performed with a 10mm expansion after simulation of a surgical vertical osteotomy line on the model in the mandibular midline region. The geometry and mesh of the bone callus were constructed. The bone callus was modelled as a strengthened region characterized by a Young's modulus corresponding to consolidated bone to predict the long-term biomechanical effect of SD. Boundary conditions for jaw closing simulations were represented by different jaw muscle load directions. The von Mises stress distributions in both joint discs and condyles during closing conditions were analysed and compared before and after SD. Stress distribution was similar in discs and on condylar surfaces in the pre- and post-distraction models. The outcomes of this study suggest that anatomical changes in TMJ structures should not predispose to long-term tissue fatigue and demonstrate the absence of clinical permanent TMJ symptoms after SD.

[Experimental research on mechanical behavior of human placenta]. / Détermination expérimentale des lois de comportement mécanique du placenta.

OBJECTIVES: Determination of mechanical properties of human placenta. PATIENTS AND METHODS: Realisation of an experimental study using 80 human placentas and modelisation of this study using a finite element numerical model. Using the inverse analysis method, research of the parameters of placenta's behavior. RESULTS: Hyper-Visco-Elastic law written by Ogden, optimized for placenta with parameters: mu(1)=0.0001881Mpa, mu(2)=-0.000240Mpa, mu(3)=mu(4)=0Mpa and alpha(1)=2, alpha(2)=-8, alpha(3)=alpha(4)=0 in static condition. DISCUSSION AND CONCLUSION: The parameters enable an approach of the mechanical behavior of the placenta. They could be used in numerical modelisation.

[Contribution of the finite element method in maxillofacial surgery]. / Apport de la méthode des éléments finis en chirurgie maxillofaciale.

The finite element method is a numerical modeling tool used in various fields in medicine and surgery such as orthopedics, traumatology, and cardiovascular surgery. But this tool also has several applications in maxillofacial surgery. We present the advantages of this method by describing its principles as well as the various fields of application in maxillofacial surgery. This article was intended to help novices understand the results of various studies using this method.

Finite element modeling for soft tissue surgery based on linear and nonlinear elasticity behavior.

New surgical techniques require fine control from the surgeon's point of view. Until recently, the necessary experience was only obtainable through traditional training protocols (using cadavers, animals, etc.). However, numerous training simulators have now been developed for use in this area. We present a new approach based on a three-dimensional finite element software and on different kinds of linear and nonlinear elastic constitutive equations that is able to predict realistic results. To classify these equations in terms of accuracy, we performed ex-vivo experimental measurements on lamb kidneys. The software has been applied to soft tissue deformation, namely lamb kidney and human uterus, and the numerical results have been compared to experimental ones.