| Objective: In our project, we using three-dimensional FEM with the assist of dynamic load to study if the change of the position and angle of All-on-4 implants influence the stress distribution of the implant and the bone tissue around it, providing the theoretical basis and model for implanting on edentulous jaw in clinic.Methods: 1. Establishing the model : Anatomical basis on a healthy elderly people with edentulous jaws specimens, scan at CBC T, medical raw date of Dicom format were read and displayed. With the assist of the softwares Mimics l7.0 and Geomagic which were used to produce 3D images, edit and process solid models of maxilla and mandible. Using software UG NX 8.5 to get the solid models of All-on-4 implant-supported fixed prostheses combining with parametars. The maxilla and mandible jaws are divided into 9 groups respectively with the situations of the different position and the angle of implants: maxillaâ… ~â…¨, mandible â… ~â…¨. 2. Three-dimensional Finite element model stress analysis: we take a dynamic finite element analysis on models with help of software Abaqus 6.12. Molars is set to 150 N and the dynamic load simulation cycle is 0.875 s. The implant and the surrounding bone stress distribution are observed.Results: 1. Successfully building the mode ls of maxilla, mandible and All-on-4 implantsupported fixed prostheses which has a greater level of similarity with clinical cases. We can make it more convenient to observe and measure the clinic cases with the help of the models, and establish the model foundation for edentulous jaws of implanting repair cases at the same time. 2. The data of jaw groups shows: the maximum stress increases at first then decreases in the groups of maxilla at the mesial and distal position of implants and the cortical, cancellous bone, which occurs during the second to fourh stage of mastication cycle. And at third stage the stress is the peak value in the dynamic cycle. The stress of cortical bone of Maxilla I distal position reach the maximum in the 9 groups. While the maximum stress increases all the time in the mandible 9 groups, and at the fourth stage the stress reach the maximum during the dynamic cycle. The stress of cortical bone of mandible VI distal position reach the maximum in the mandible 9 groups. 3. Combing the stress data of the groups with statistics analysis we can get that the best position for this case in the models are maxilla â…¦ and mandible â…¤.Conclusion: 1. This study applies the three-dimensional finite element method which establish models of All-on-4 fixed prostheses has a higher similarity with clinical cases. It can be used in the clinical trials, and provide the foundation for toothless jaw stress analysis for clinical. 2. We make the dynamic load to simulate mouth chewing process, and take stress analysis on the finite element model of fixed denture, then we obtained implant-bone interface stress value and stress distribution under different load stage, which is closer to the clinical situation, so it is significant in occlusal adjustment in clinical.3. The different implant position of the All-on- four fixed prostheses is the vital factor that influence the stress around the bone tissue. We choice the different implant position according to the bone shape and bone mass. |
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