| The stress distribution of bone around dental implant under physiological load is investigated by 3D FEA. The calculative result can provide important data for the design and clinical application of dental implant. But the reliability and application of results greatly depend on the accuracy and load's method of model. In this study, based on CT data and computer technology of segmental processor, the accurate CAD and FE models of four typical teeth in mandible, which is full of clinical representation, are rebuilt. The stress distribution of bone around implant in diverse teeth models are analyzed combined with occlusive measurement of load method. At the same time, as for the difficult problem which there is structural limitation of dental implant possibly leads to bone pathological absorption and finally make the implant be failure, we put forward a new-type dental implant, which it transfer load through the bolt structure. The stress distribution of new design and the influence of relevant structural parameters are studied by FEA. The new structural design has been evaluated and optimized in definite bone condition. These conclusions are as follows:1) The FE models established by CT data exactly reflect the complicated configuration, which isn't symmetrical between the buccal side and lingual side in mandible. Because of the angle between the direction of the physiological load and vertical axis of implant, so the stress distribution of bone is influenced greatly byload's angle. So the peak stress of bone at the lingual side is two or three times as big as that at the buccal side. With regard to the second former molar, fang and incisor, they can support the physiological load of 300N, 180N, and 120N respectively by the rehabilitation with cylindrical dental implant, so they can basically restore their physiological functions. As for the second molar, it can only support the load of 100N because of the too large load's angle. Therefore, implant is suggested to be embedded through the direction of the physiological load. In this condition, It can endure physiological load of 250N and meets common need of clinical application.2) The FEA result of stress distribution of new-type dental implant shows that: Compared with traditional implant, the stress concentration in the bone of implant cervix has been largely reduced and it decreases about 2/3. The key factor is that the new design transfers load through different method, and the load was firstly transferred stress straightly to the cancellous bone and then to the cortical bone, so the stress concentration of the cortical bone is effectively decreased. The new-type implant not only reduces the cervix stress of implant, but also adjusts the whole stress distribution of implant. So the stress distribution is more even and the stress concentration and stress shield are both reduced in favor of the long-term stability of dental implant.3) The new-type dental implant has been designed based on the mechanism of bolt structure. The relation between the key factor-gap and stress distribution has been researched and find out the depth of gap influences obviously stress. With the depth's increasing, the cervix stress gradually reduces. However, the diameter of gap hardly affects the stress. On the other hand, the relation between the shape, external structure, material's properties, load's method and cervix stress distribution of implant have been analyzed. The optimized result is: cylindrical implant with 60° screw and TC4 implant material. Furthermore, the own stress distribution of dental implant has been investigated and its peak stress is under the subdued intensity of material. So it meets the need of intensity and can be safely used in long period. |
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