Three Dimensional Finite Element Analysis Of Implant Anchorage In Maxillary Extraction Space Closure

Objective:In order to study the mechanical characteristics of the maxillary anterior teeth and periodontal ligament when the maxillary extraction space is closed with the implants and traction hooks,we establish a three dimensional finite element model of the maxilla,maxillary dentition,periodontal ligament,archwire,bracket,traction hook and implant anchorage,studying the stress distribution of the root and periodontal ligament of the maxillary anterior teeth and the displacement of the crown of the maxillary anterior teeth when the maxillary extraction space is closed with the different height of implants and the different length of traction hooks and increasing the vertical pressure of the anterior teeth.Methods:1.Establish a three dimensional finite element model of the implant anchorage for maxillary space closure: A patient who is already in the stage of closing the extraction space is selected.CBCT is used to scan the data and save it as DICOM file.The DICOM file is introduced into the Mimics 19.0 software to extract the model of maxillary dentition and alveolar bone.Then use Geomagic Studio 10.0 software to optimize the model.Solidworks 2018 software was used to establish brackets,implants,archwire,and traction hooks.Finally,the finite element analysis software ANSYS 16.0 was used to establish a three dimensional finite element model of the implant anchorage for maxillary space closure.2.Three dimensional finite element analysis of the maxillary extraction space is closed with the height of implants and the length of traction hooks: The implants are implanted between the second premolar and the first molar on both sides of maxillary,and the heights are 6mm,9mm,and 12 mm from the archwire.The position of the traction hook is between the brackets of lateral incisor and the canine and the length of traction hooks are 2.5mm and 7.5mm.A simulated orthodontic force,which is 1.5N,is loaded between the implants and the retraction hooks.The stress distribution of the root and periodontal ligament and the displacement of the crown of the six methods are analyzed.3.Three dimensional finite element analysis of increasing the vertical pressure of the anterior teeth when the maxillary extraction space is closed: Based on the model of experiment two,implant anchors are implanted in the anterior area of the maxillary,and the locations are: between the maxillary incisors;between the maxillary central and lateral incisor;and between the maxillary lateral incisor and the canine.The height of the implant in the posterior tooth area is 6mm from the archwire and the height of the traction hook is 2.5mm.A total of 50 g vertical pressure in the maxillary anterior teeth area is added to analyze the stress distribution of the root and periodontal ligament and the displacement of the crown of the above four methods.Results:1.A three dimensional finite element model,including maxilla,maxillary dentition,periodontal ligament,archwire,bracket,traction hook and implant anchorage,is successfully established.2.In the process of closing the maxillary extraction space with implants,when the height of implant is the same,as the length of the traction hook increases,the tendency of distal displacement of the crown decreases,the tendency of lingually decreases,and the tendency of extrusion decreases.When the length of the traction hook is the same,as the height of the implant increases,the tendency of distal movement of the crown decreases,the tendency of lingually decreases,and the tendency of extrusion decreases or increases first and then decreases.3.Compared with no implant anchorage in the maxillary anterior teeth area,the maxillary anterior teeth with implant anchorages have a reduced tendency to move distally and lingually,the tendency of lip displacement increases,the tendency of extrusion of the crown decreases and the tendency of intrusion increases.Conclusions:1.The model of three dimensional finite element analysis of different anchorage conditions in maxillary extraction space closure accords with the actual condition of the patient,and it can provide a good experimental basis for the later finite element analysis.2.In the process of closing the maxillary extraction space with implants,the high implant anchors and long traction hooks are suitable for patients with deep overbite,and the low implant anchors and short traction hooks are suitable for patients with a tendency of open bite.3.In the process of closing the maxillary extraction space with low implant and short traction hook,after increasing the vertical pressure of the maxillary anterior teeth,the displacement of the anterior teeth decreases,the positive torque of the anterior teeth increases,and the anterior teeth will be intruded during the process of closing the extraction space.