Three-Dimensional Finite Element Analysis Of Maxillary First Molar Depressed By Micro-Implant Anchorage Combined With Segmental Arch

Objective: To study the influence of different anchorage methods on the displacement trend of maxillary posterior teeth and the hydrostatic distribution of periodontal membrane when the maxillary first molar was depressed,and the influence of segmental arch on the displacement trend of maxillary posterior teeth and the hydrostatic distribution of periodontal membrane.The purpose of this study is to provide reference for more efficient depressed-maxillary first molar in clinic.Methods: 1.A 23-year-old female volunteer was selected and scanned CBCT after obtaining informed consent.The data was extracted by Mimics.The three-dimensional models of maxillary posterior teeth and maxilla were established by Geomagic Studio.The models of brackets,buccal tube,lingual buckle,arch wire,chain rubber band and microimplant were established in NX,and all the models were integrated.Finally,Ansys was used to set material parameters,grid,boundary,coordinate system and load conditions.A three-dimensional finite element model was established to depress the maxillary first molar.two.The experiment was divided into ten working conditions,from condition 1 to condition 5,two implants were implanted between the buccal root of the first molar and the buccal root of the second molar,and between the second premolar and the palatal root of the first molar.a chain rubber band connects two implants across the crest surface of the first molar.In condition 2,two implants were implanted between the buccal root of the first molar and the second molar and in the area adjacent to the middle palatal suture,and the chain rubber band was connected with two implants across the first molar surface.The chain rubber band connects the buccal buccal tube of the first molar with the buccal implant,the palatine lingual buckle and the palatal implant,respectively.In condition 4,on the basis of condition 1,an implant was added between the second premolar and the buccal root of the first molar,with a total of three implants,a chain rubber band connecting the buccal implant and the buccal tube,the palatal implant and the lingual buckle.In condition 5,on the basis of condition 4,an implant was added between the first molar and the palatal root of the second molar,a total of four implants were added.The chain rubber band connects the buccal buccal tube of the first molar and the buccal implant,the palatine lingual buckle of the first molar and the palatal implant respectively.The total force generated by the implant and chain rubber band is 150 g.The segment bow group was from condition 6 to condition 10,and 0.013 inch nickel-titanium arch wire was added as segment arch on the basis of condition 1 to 5,respectively.3.The changes of the initial displacement of the maxillary posterior teeth,the initial displacement of the landmarks of the first molars,the equivalent stress and the hydrostatic pressure of the periodontal ligament of the first molars under ten working conditions were analyzed.Results: In the implant group,the displacement of other teeth was significantly smaller than that of the first molars,and the first molars were significantly depressed,with the largest depression under working condition 5,the largest palatal movement in working condition 5 and the largest mesial movement in condition 4.The Z-axis displacement of the first molar in the segmental arch group was significantly larger than that in the implant group,and the adjacent teeth had more obvious elongation and palatal tilt movement,which was less than that of the first molars.The displacement of the first molar in the segmental arch group was larger than that in the implant group,and the buccal displacement in the seventh Y axis was the smallest.The maximum equivalent stress of the periodontal ligament of the first molar under condition 8 and condition 9 exceeds0.026 Mpa,which may cause periodontal tissue damage.The maximum compressive stress of periodontal ligament in all conditions exceeded the threshold that might cause root resorption,and the maximum compressive stress in the periodontal ligament of the first molar was concentrated in the apical and neck.Conclusion: 1.With the increase of the number of implants,the suppression efficiency is improved,and the ten reduction efficiency is the highest in all operating conditions.two。.The segmented arch can resist the palatal inclination trend caused by simple implant pressure on the first molar,and improve the reduction efficiency,and condition 7 is the closest to vertical depression.3.In clinic,a depressing force of less than 150 g can be selected to reduce the risk of root resorption.4.In clinic,the segmental arch and implant should be flexibly selected according to the actual situation.