| Objective To discuss the stress of the structure changing of implant on the implant-bone interface under different condition. Looking for the theory evidence of the design and clinical application of the new structure implant.Methods A simulated bone block and two kinds digital model of implant were established by Pro/E software. The Ansys Workbench software was used to compute the trends of stress within deferent bone condition and loading situation. Concluding the structure of human mandible, a 8*16*22mm cuboid was built, which has a 3mm thick cortex bone on the up and bottom surface. The characteristic of ?-class bone was selected to use in the spongy bone which satisfied implant operation most. Then build two kinds of 5.5mm diameter implant. Model A(non-tread sandwich implant) and model B(non-tread traditional implant).,Four parts of experiment were designed in connection with model A. and Model B. Part 1, fix the thickness of the filling part,then change the elastic modulus(E) and Poisson ratio(?) of it. 50 groups of Elastic modulus and poisson ratio are randomly chosen by computer in the range of common materials. Analyze the variation tendency of max equivalent(Max EQV) on the implant-bone interface within two changing variables(E&?), under a vertical loading and a 45°slope loading. Looking for the relationship between the two variables and the Max EQV with a relativity matrix. Part 2, divide the nine kinds of models into groups by the core height(h) and the ratio of the thickness of outer shell(d) and filling part(D). Divided by h, analyze the Max EQV on the implant-bone interface under a vertical loading and a 45°slope loading with a changing “d:D”. Then divided them by d:D, analyze the Max EQV with a changing h. Part 3, basing on the foregoing data,chose a group data of E, ?, h, d:D when the Max EQV behaving most suitable.Analyze the variation tendency of Max EQV under the vertical loading, 45°slope loading and the chew-simulate loading between the sandwich implant(model A) and the traditional implant(model B) with a contrast test.ResultsUnder a vertical loading, the maximum Von-Mises stress of model A was 17.54%lower than model B;under a 45°slope loading,the maximum Von-Mises stress of model A was 2.59% lower than model B,and it was shown a lower stress especially on the buccal side; under the chew-simulate loadings, the maximum Von-Mises stress of model A was lower than model B at all degrees. The biggest difference(0.3532MPa)appeared at ?=12°(?is the angle of force and the implant axis),and it gradually reduced after?>12°. At the same time, model A had a wider degree application on the index of bone-regeneration stress and bone-keeping stress than model B.Part 1, within 50 groups of E&? of the characteristic of filling part,the lowest Max EQV appeared at the group of ? =0.33;E=10505MPa. The relativity matrix showed that Elastic modulus affected Max EQV more than Poisson ratio. Based on the recent result, designed a further experiment. Stabled the Poisson ratio(?=0.33),changing the Elastic modulus randomly, then found that the Max EQV had a growing linear relationship with the Elastic modulus. Part 2, divided by h: according to the model group of h=0mm, the sandwich implant model showed a higher Max EQV than the traditional implant model under all kinds of situation, with all groups of d:D at the same time. According to the model group of h=2mm, it showed the lowest Max EQV when d:D equals to 2:1. Part 3, four data d:D=2:1, h=2, E=9500, ?=0.33 was given to the model A,appeared model A10. As a control group, a traditional implant Model B was built. As a result, the Max EQV under vertical loading, 45°slope loading and chew-simulate loading of the model A10 were lower than the model B of all situations.Conclusions The new structure implant can decrease the max stress on the implant-cortex interface, and make the stress distribution better at the same time. Therefore, it has got a certain clinical application value thanks to the reduce of the risk of bone resorption. |
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