The Finite Element Analysis Of Displacement And Stress Concerning The Corticotomy-assisted Controlled Tipping Of The Maxillary Central Incisor

ObjectiveThis study,based on 3D image data of right maxillary central incisor obtained by microCT scanning and combined with Mimics.CATIA,Abaqus and other software,is to construct a 3D finite element model with a lip inclination of 20 degrees(maxillary central incisor-periodontal ligament-cancellous bone-cortical bone),and to compare the effects of different types of corticotomy on the displacement and stress of the teeth and periodontal tissues in the process of controllable tilting of the maxillary central incisor by means of the finite element analysis(FEA).The purpose of this study is to provide a theoretical basis for the clinical use of corticotomy to accelerate the biomechanical control of the anterior teeth.Methods(1)In this study.MicroCT scanning is used to obtain the imaging data of the right maxillary central incisor and alveolar bone of the fresh human cadavers,and the data is then imported into Mimics17.0.where 3D models of the central incisor and periodontal ligament is obtained according to the grey level of tissues.Smooth and establish the model of NURBS of the central incisor and periodontal ligament in Geomagic Studio 12.Then introduce them into CATIA V5,draw alveolar bone based on anatomical data.Next,divide alveolar bone into two parts,cancellous bone and cortical bone.Last,a four-part model was assembled in CATIA V5,which contains the central incisor,periodontal ligament,cancellous bone and cortical bone.Rotated the model 20° counter clockwise along the Z axis.(2)Import the above experimental model into CATIA V5and then draw different types of cortical incision models according to the commonly used cortical bone incision.Further,import the control model into Abaqus,define material properties,divide the grid,set the contact relationship and apply the load.In this study,we set the force of retraction 1N,after repeated attempts,the experiment finally determined the moment is 8.18Nmm for controllable tilting movement of the right maxillary central incisors with a lip inclination of 20 degrees;M/F value is 8.18.After the experimental groups are made the corresponding setting,observe and record the changes of tooth displacement and stress,the displacement of cortical bone and the stress of periodontal membrane.Results(1)With 3D image data obtained by MicroCT scanning,combined with Mimics,CATIA,Abaqus and other software,the 3D finite element model of right maxillary incisor with a lip inclination of 20 degrees was established,which contains458990 units and 780283 nodes.(2)The right maxillary central incisor with a lip inclination of 20 degrees obtained a controllable tilt movement under the force system of 1N adduction and-8.18Nmm torque.(3)Compared with the control group,the maximum displacement of central incisor and alveolar bone increased after corticotomy.The initial maximum displacement of teeth and cortical bone increased less.If corticotomy is only applied near or far the middle,without the apical of labial or palatal,while the maximum displacement of teeth and cortical bone was significantly increased after the incision of the upper lip and(or)the palatal root.(4)Compared with the control group.the initial maximum stress of the tooth root decreased after corticotomy.The effect of corticotomy of labial on the maximal stress of the tooth is less than that of the palatal.(5)The maximum stress of the periodontal ligament was located in the lingual side of the maxillary incisors.There was no significant effect of cortical incision on the initial stress of the periodontal ligament.Conclusion(1)A 3D finite element model with high accuracy to meet the experimental requirements is established,which is based on the 3D image data of right maxillary central incisor and periodontal membrane obtained through MicroCT scanning combined with the alveolar bone established in CATIA.(2)The M/F value of the maxillary incisor with a lip inclination of 20 degrees was-8.15:1 when controllable tilt movement is allowed.(3)After the perform of corticotomy.the maximum initial displacement of teeth and bone cortex increased;root maximum initial stress decreases;periodontal ligament maximum initial stress had no obvious change in the process of controllable tilting movement of the maxillary central incisor.