Three-dimensional Finite Element Analysis Of Intrusion Of Maxillary Anterior Teeth By Miniscrews With Clear Aligner

Objective:The aim of this study was to assess the displacement and stress distribution of maxillary incisors and canines when addressed to different models of intrusion mechanics using miniscrews by constructing a three-dimensional finite element model of maxillary bone and teeth,clear aligners and miniscrews,which provide the theoretical basis for clinical application and scientific guidance.Methods:Cone-beam computed tomography maxillary scans of a young woman were available to us.we constructed a 3-dimentional finite element model,including maxillary bone and teeth,clear aligners and miniscrews,by Mimics,Geomagic Studio,and HyperMesh.The force application were: Working condition 1,the miniscrew was placed between the roots of the central incisor and the force was applied at the same height as center of the crown between the central incisors.Working condition 2,the miniscrews were placed bilaterally between the roots of central and lateral incisors and the force was applied at the same height as center of the crown between the central and lateral incisors;Working condition 3: the miniscrews were placed bilaterally between the roots of lateral incisors and canine and the force was applied at the same height as center of the crown between lateral incisors and canine.Working condition 4: the miniscrews were placed bilaterally between the roots of lateral incisors and canine and the force was applied at the same height as center of the crown between the central and lateral incisors.Except for the first model,the intrusion force was 0.98 N,and the other three models were 0.49 N bilatterally.The initial displacement trend and stress distribution of the teeth were analyzed under four working conditions.Results:1.A three-dimensional finite element model of maxillary dentition-maxillary-clear aligner-micro-miniscrews was constructed.2.In clear aligners treatment,under the four working conditions,during the process of maxillary anterior teeth intrusion with miniscrews,each anterior tooth's tendency of tipping movement is not completely consistent when they were under the same mechanical load.3.In clear aligners treatment,under four conditions,the displacement of the incisal margin was greater than the apex,and the difference between the displacement of the crown and the root was different: the incisors : condition three> condition two> condition one> condition four;The difference of the labial displacement of canine crown and root between the four conditions is small,and the condition four is the smallest.4.In the clear aligners treatment,the vertical displacement of the incisal margin was greater than the apex in the four conditions,and the vertical displacement of the apex of the maxillary incisors were the smallest in the four conditions.5.In clear aligners treatment,under four working conditions,the Von-Mises stress was mainly concentrated on the labial side of apical,the neck of the root labial side,the incision margin,and the lingual side of the crown.In condition four,the Von-Mises stress concentration area was relatively the smallest,the stress distribution is more uniform,and the maximum stress value of the incisor was also the smallest.Conclusion:1.Through CT scanning and the application of reverse engineering software,a three-dimensional finite element model with complete structure,high simulation and good geometric similarity can be constructed for materials with complex structures and diverse geometric shapes.2.In clear aligners treatment,labial tipping of maxillary anterior teeth is reported in all working conditions.the smallest labial tipping trend occurs and the risk of root resorption is lower when the miniscrews were placed bilaterally between the roots of lateral incisors and canine and the force is applied at the same height as center of the crown between the central and lateral incisors3.In clear aligners treatment,while the miniscres intrude the anterior teeth,the anterior teeth have a tendency to scatter.The clear aligners need to better wrap the anterior teeth and reduce the side effects.