Biomechanical Analysis Of The Human Temporomandibular Joint During Clenching With The Two-dimensional Meshless-FE Coupling Method

The temporomandibular joint(TMJ) is the most complicated andsubtlly used of all the body joints. In TMJ, the articular disc is the mostimportant structure. Therefore, the biomechanical environment in theTMJ, especially the articular disc, is a key to understand the origin andprogression of TMDs. Because numerical simulation is more effective inanalyzing the stress distribution of TMJ, the finite element method(FEM) is extensively used. But proper meshing of the analysis domain in FEMespecially for complex or irregular shapes, e. g. TMJ, can be difficult andlaborious. Moreover, in FEM the obtained stress field has a low degree ofcontinuity, which degrade efficacy of simulation. Recently, a new familyof numerical methods globally coined as meshless or mesh-free haveundergone intensive researches. Various Galerkin-based meshlessmethods have been developed or investigated to solve mechanicsproblems without the use of a structured grid. These meshless methodsemploy MLS approximation of a function that permits the resultant shapefunctions to be constructed entirely in terms of arbitrarily placed nodes. Itis more accurate and convenient and has solved many problems whichFEM can not solve. Nevertheless, a troublesome job within the meshlessmethod is the enforcement of essential boundary conditions. Hence, weemployed meshless-FE coupling method in biomechanical analysis of theTMJ and the results between meshless-FE coupling method and FEM wascompared and analysed. The purpose of this study is to assess theaccuracy of our meshless method and introduce a new and effectivenumerical method in biomechanical analysis of the TMJ.Partâ… The reconstruction of two-dimensional meshless-FE couplingmodel of TMJMaterials and Methods: The three-dimensional finite element model ofthe mandible including the TMJ was identical to that used in the team of Yin Xinmin. As the TMJ was bilaterally symmetrical, only the right partwas included in this study. This three-dimessional finite element modelwas opened in Marc2003. A two-dimensional topography of TMJ wasoutputted with a sagittal cut through the center of the condyle.Afterwards, this topography was imported into Ansys8.0. Then the modelwas discretized into FEs tetrahedral over again.It was conserved as model1. The elements of glenoid fossa, condyle and mandibular rames and thenodes of the surface of articular disc was kept invariable. Interior ofarticular disc was discretized with only a set of nodal points but withoutany mesh constraints. Then a two-dimensional meshless-FE couplingmodel was developed. It was conserved as model 2.Results: Model 1 was a two-dimensional finite element model includingglenoid fossa, articular disc, condyle and mandibular rames, containing1059 elements and 1189 nodes. Model 2 was a two-dimensionalmeshless-FE coupling model, consisting of 182 meshless nodes.Conclusion: On the basis of finite element model, a complextwo-dimensional meshless-FE coupling model of TMJ can be constructedmore precisely by means of technology of discretizing a set of nodalpoints.Partâ…¡: Biomechanical analysis of the human TMJ with thetwo-dimensional meshless-FE coupling methodMaterials and Methods: The simulations to two models started with the jaw in closed position, followed by a displacement of the condyle againstthe glenoid fossa in a direction corresponding to the estimated directionof the joint reaction force. The two-dimensional finite element model wasanalyzed using the Ansys8.0 finite element software. Thetwo-dimensional meshless-FE coupling model was analyzed using aself-developed processor. The result datas were input into the Ansys8.0and then the stress distribution contours of the TMJ were obtained.Results: The stress results between meshless-FE coupling methods andfinite element method were compared and analysed. They were found invery good agreement. The values of the Von Mises stresses were less onthe glenoid fossa than on the condyle and the articular disc. In thearticular disc, high von Mises stresses were seen at the intermediate zoneand the bilaminar region. But result of meshless-FE coupling method ismore refined.Conclusion: The stress results between meshless-FE coupling methodsand finite element method were found in very good agreement. But resultof meshless-FE coupling method is more refined.