| Objectives:The aim of this study was to exeplore the effect of different implant depth, abutment with different height through gingiva and abutment with different angles on the stress, and to provide theoretical basis for the clinical application of platform switching implant.Methods:Using Solidworks2007 mapping software, we established the model of implant-abutment in typeⅡbone area with different implant depth, and with abutments of different height through gingiva. The model was loaded vertically and 45-degree from the abutment using Ansys-workbenchll.0 finite element analysis software. Then we analyzd the stress distribution on conditions of different implant depth(0mm,1mm,2mm,3mm,4mm)with different abutment height through gingiva (0.75mm,1.5mm,3.0mm,4.5mm,6.0mm), giving preliminary appropriate implant depth. On basis of this, the model was loaded parallelled or with a-45°-angle from the abutment with different abutment angles(7.5°,15°,22.5°,30°,37.5°). The results were analysed with SAS8.2 statistical software using ANOVA.Results:1. The stress of implant with platform switching mainly focus on the implant-abutment;2. The difference of the maximum stress of cortical bone and implant-abutment in different implant depth is very significant (p<0.0001),but that of the cancellous bone is not so significant (p<0.05); When the implant depth is within 2mm in cortical bone, the maximum stress of implant-abutment, cortical bone and cancellous bone are all suitable; 3. The difference of the stress on cortical bone and implant-abutment with dif ferent height of the abutment through gingival is significant (P<0.05) but that of cancellous bone is not so significant (P>0.05). If other factors are equal,the maximum stress on the implant-abutment, cortical bone and cancellous bone will remain in a steady state when the height of the abutment through gingival is 3.0mm-6.0mm;4. The difference of the maximum stress on implant-abutment, cortical bone, cancellous bone with different abutment angle is significant (p<0.05). With the increase of the abutment angle,the maximum stress of cortical bone and cancellous bone will have a growthing trend in most cases. But as the maximum stress of implant-abutment,when the abutment angle is less than 7.5°, the change is not obvious, but when the angle is greater than 7.5°, it will increases with the angle of the abutment rapidly;5. The difference on the stress distribution of implant-abutment, cortical bone, cancellous bone using different loading way is significant(p<0.0001); when straight abutment loaded on oblique,The maximum stress of all the three will increase significantly than that of the vertical loaded;when abutment with angle is used, If the implant depth is shallow, the oblique load will not increase the maximum stress of cancellous bone significantly, but no matter how it will increase the maximum stress of cortical bone and implant-abutment significantly, in particular the angle of the abutment is small.Conclusions:1. The analysis of stress using FEA is simple and feasible in the study of platform switching;2. To avoid the stress concentrate excessively on the bone, the implant depth should be controlled less than 2mm under the cortical bone in the range of this experiment;3. If other facters are under certain conditions, the maximum stress of cortical bone and implant-abutment have an increasing trend as the increasing of the height of the abutment through gingiva, but the change of cancellous bone is smaller. Yet all of the three maximal stress will have little change when the height of the abutment through the gingival is higher than 3.0mm;4. To prevent too stress concentrate on the bone, abutment with angle especially with large angle should be used as little as possible;The lateral force should be reduced as far as possible to avoid high stress concentration leading to bone resorption. The stress concentration caused by abutment angle should be avoided to be added on the effect caused by loading angle. |
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