Three Dimensional Finite Element Analysis Of Micro Implant Anchorage In Maxillary Anterior Teeth Retraction In The Process Of Continuous Change Of The Angle And The Length

Objective Using three dimensional finite element method to establish the threedimensional finite element model of the micro implant-maxilla-maxillary dentition-straight wire appliance,exploring the influence of micro implant-bone interface stress distribution,when the implanting angles and lengths continue changing in the process of adduction of maxillary anterior tooth,in order to provide the reference for clinical selection of micro implant implantation angles and lengths.Methods One clinical sample of upper arch protrusion taken for example,using cone beam CT(CBCT)scan to get the data of maxilla and maxillary dentition,and then using software of Mimics17.0、Geomagic Studio12.0 and Siemens NX8.5 to create structural integrity and geometric similarity three-dimensional finite element module which include straight wire appliance and all kinds of micro implant in the cases of three dimensional model.Put the CBCT data import Mimics17.0,through the operations of screening of grey value、regional growth、the selected image、edit 2D mask、three-dimensional reconstruction、smoothing processing for three dimensional reconstruction of the model of the complete tooth、cortical bone and cancellous bone,and then put the.stl format the model output import Geomagic Studio12.0.In the Geomagic Studio12.0,by removing nail substance、refine edge、incresing surface mesh to optimize the model of the.stl format more,the models of straight wire appliance and different lengths of micro implant established according to precise surface wizard generated Nurbs surface,which in turn generate three-dimensional entity model,and with.stp format export to Siemens NX8.5,carry on transformation at last.Giving the material properties of the tooth、cortical bone、cancellous bone、straight wire appliance and micro implant in Ansys16.1 analyses the Von-Mises stress distribution(Von-Mises)of the implant and the surrounding cortical and cancellous bone when the loading force is 200g(1.96N)and the length of implant to 7mm、7.5mm、8mm、8.5mm、9mm and the angle to 45°、60°、75°、90°.Results Under different implant angles,when the loading force of micro implant is 200 g and the implant length of micro implant anchorage is 8.0mm-8.5mm,the Von-Mises stress of cortical bone、cancellous bone and micro implant reach the minimum.And under different implant length,with the change of the implanted angels,the performance characteristics of micro implant、cortical bone、cancellous bone are different.Due to the Von-Mises stress of the cancellous bone are much smaller than the Von-Mises stress of micro implant and cortical bone,it could be neglected.If we only consider the Von-Mises stress of micro implant and cortical bone,the Von-Mises stress of them reach the smallest when the implant angle is 75°with different implant length.Conclusions The patient whoes row of neat and level off the dentition has upper arch protrusion,using micro implant to adduct maxillary anterior tooth.The best implant length of micro implant anchorage adducting upper anterior tooth is 8mm-8.5mm and best embedded angle is 75°when the loading force of micro implant is 200 g.