Biomechanical Study of Changes in the TMJ During Mandibular Functions

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1. The Positional Relationship Between the Condyle and Glenoid FossaeThree-dimensional configuration of the TMJ was conducted with tomograms by use of a personal computer system. The shortest distance between the condyle and glenoid fossa was measured in the model. As a result, it was shown that the present technique had an enough accuracy and was an available method to evaluate the relation of the condyle to the glenoid fossa in orthodontic patients with temporomandibular disorders.2. Biomechanical Properties of the TMJ DiscArticular discs derived from eight adult dogs were used for tensile tests. The results revealed that 1) the disc exhibited non-linear stress-strain relationships, 2) the non-linear curve could be described by two straight lines connected at a stress of 150gf/mm. Thus, it was indicated that the disc experienced different two elasticity according to stresses applied to the disc and that its biomechanical behavior was different in different areas of the disc.3. Constr … More uction of Analytical Model of the TMJA human dry skull was divided into transverse planes parallel to the Frankfort horizontal plane. Photographs were taken of sections and were traced on acetate papers. Then, two-dimensional discretization was performed on the diagrams from the sections. Finally, all the diagrams were built up vertically to develop a model. The model consists of 2082 nodes and 1340 solid elements.4. Stress analysis in the TMJThe model developed was used for stress analysis by means of the finite element method (FEM). Before the analysis, muscle force was integrated in the model, simulation clinical movements of the mandible. For the analysis, an approximately 500 gf force was apllied to shift the mandible in the clockwise direction. As a result of analysis, almost uniform tensile stresses were induced in and around the condyle and glenoid fossa. Tensile and compressive stresses were produced at the anterior and lateral-posterior regions of the articular disc.Thus, it is shown that 1) the nature of stress distributions in the disc was different in different areas of the disc, even in loading with simple force applied to the mandible, 2) the magnitude of stresses in the articular disc was reduced in comparison with actual biting and chewing forces, 3) a force system to shift the mandible in the clockwise direction might induce easily medio-anterior reduction of the disc. Less