| The improvement of malocclusion is achieved by the mechanical force with a certain magnitude and direction through certain orthodontic appliance. Stress-strain distribution in the periodontal ligament and the surrounding alveolar bone which determines the mode of tooth movement help clinic orthodontist master the effective way of tooth movement. According to Newton's third law, the force added to the orthodontic appliance will inevitably cause a force with the same magnitude and opposite direction. The counterforce must be resisted by a certain kind of organ or instrument such as headgear and TPA. Two orthodontic systems, Micro-implant anchorage (MIA) and Forsus appliance are selected.Micro-implant anchorage (MIA) system is the special screw made of pure titanium material with good bio-compatibility. The screws were inserted into the alveolar ridge or upper and lower jaw bone of different site to get orthodontic treatment. In recent years, a great number of orthodontic doctors pay close attention to fixed appliance of Forsus, for such appliance is small in size, has more durable and homogeneous elastic force and easy to control too. What's more, the installation is much easier and the course of treatment is shorter in general. In a word, fixed appliance suggests the new developmental trend of the orthopedic treatment appliance.Numerical simulation analysis is one important means in oral biomechanical study, and it has been widely used in biomechanical study. By using the simulated analysis of the MIA system and the Forsus orthopedic force system, the different mechanical effects can be analyzed under different anterior guidance operating conditions, and the analysis improves the clinical application of the appliance as well.In this dissertation, on the basis of the research on the application of MIA and the clinic treatment, elastic-viscoplasticity of bone is discussed. The UMAT program considering elastic-viscoplasticity constitutive relationship of material is written, combining with CT scan technique and FEM software, a numeral MIA-teeth-maxilla three-dimensional model was established. The dynamics response process of bone was investigated after the mini-screw inserted. A numerical analysis was presented for stress and strain transformation process in maxilla when under the orthodontic loadings. It provide an important scientific criterion for the optimize of MIA. The main work and conclusions in this dissertation are as follows: â‘ Advancement what have been made in recent years about orthodontic biomechanics was reviewed in this dissertation. Finite element method in orthodontic numerical simulation was summarized. The application and investigation of MIA in orthodontical treatment were reviewed as the focus.â‘¡Use elastic, viscous and plastic parts to construct a elastic-viscoplastic constitutive relation of bone. Especially, under loading of orthodontic force, constitutive model of bone considering timing characteristics is given out.â‘¢By CT scan technique, Mimics and ABAQUS, a new modeling method was presented. A reality MIA-tooth-maxilla three-dimensional model was established. The geometry comparability of model was improved in the extreme. And a new method to construct maxilla and teeth model quickly was explored. On the basis of full considering the change of time and space properties of MIA,teeth and maxilla, emphasis is on timing characteristics of bone, biomechanical progress of MIA,teeth and maxilla with orthodontic time increasing is discussed.â‘£A 3D model of Forsus-Dent-uperand lower jaw-TMJ with some visvelasto-plastic characters is built with isotropic,non-linearity and elastic- viscoplastic characteristics in the study. The mechanical behaviors of dentition, jaws and TMJ are studied by finite element method. The stress and displacement of dentition, jaws and TMJ are mainly researched in the study. Base on what is mentioned above, the paper recommend the load angle range of Forsus and scope of condylar reconstruction. |
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