| That the complex structure of the human oral,the irregular shape of the mandible and soft tissue,the mandible movement system involves the entire mouth,and the high standard of the experiment apparatus,are the problems of modeling and mechanical analysis of mandible.Therefore,in this paper,the biting force was measured,a complete mandible model was established,the mandible movements was simulated with finite element analysis,and the influence of contact area and interference on the mandible containing the implant was considered.Some medical experiments that are harmful to the human can be simulated by finite element analysis,Clinical treatment of oral diseases and optimal design of medical devices is also based on the finite element analysis.With the public focus on oral diseases and the need for implants,oral biomechanics is rapidly evolving.The main research contents of the thesis are as follows:(1)Based on the test method of the measuring device of biting force on the market,a self-made measuring device of biting force was developed,which has the characteristics of simple operation,high repeatability.The biting force of 8 subjects was measured on a single tooth and a intercupided occlusion(two secondary mandible incisors).The accuracy of the measuring instrument was verified by comparing data and literature.The data of biting force was counted and analyzed by gender,left and right sides,and position,which proved data reference for the subsequent finite element analysis.(2)The model of mandible and dentition was extracted by the reverse modeling software Mimics and Geomagic from the CT slices.By further segmentation and shape optimization of organize and bone,the final accurate three-dimensional mandible model was obtained,including cortical bone,cancellous bone,periodontal ligament,teeth,and disc.The mandible model was meshed and endued material property to provided a model basis for the subsequent finite element analysis.(3)The measurement experiment was simulated with FEA.The boundary conditions was set and simplified according to the principle of mandible movement,and boundary condition parameters was further refined through the reference literature to make the finite element model closer to the experimental conditions.According to the stress characteristics of each bone and tissues,an accurate finite element model can be obtained.Besides,the contact pressure and friction force on the crown during occlusion and the value and the direction of the resultant force was obtained.It can be obviously seen that the crown is mainly subjected to the positive pressure in the long axis direction and a little tangential force in the vertical long axis direction.(4)The biting force,which was calculated the finite element,was applied on the local oral model to explore the influence of the interference and the contact area between the first implant and its natural adjacent teeth on the mandible.And a Optimization of the relationship can be drew based on the result of FEA.According to the stress analysis,some conclusions can be drew that the contact area and the contact interference had little effect on the stress distribution of the mandible,but the contact area had a great influence on the stress value,while the contact interference had little effect on the stress value.It is recommended that the first molar implant has a small area contact area with the its adjacent teeth(the contact area with the second premolar is 1.772 mm~2~5.295 mm~2,and the contact area with the second molar is 2.095 mm~2~6.58 mm~2),it is effectively to distribute the load implant suffered,especially to reduce the stress generated by the lateral load when the first molar implant has a small area contact with its adjacent teeth.It could avoid a excessive stress in the periodontal ligament and alveolar bone around the natural teeth;The tightness should not be too large(the value of interference is 0~0.03mm),which can reduce the rate of food plugging and not increase the stress of bone tissue in the implant area. |
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