A Three-dimensional Finite Element Study On Horizontal “Bowing Effect” While Closing Space Using Customized Lingual Orthodontic Appliance

Objective:To establish a three-dimensional finite element model of e-Brace customized lingual orthodontic treatment for maxillary anterior teeth retraction.Under the action of mini-screw,the horizontal “bowing effect” mechanism of the traction arm in different positions and lengths during maxillary anterior teeth retraction was discussed.Methods:A 26-years-old man without orthodontic treatment was selected as the model object.A three-dimensional finite element model including e-Brace customized lingual orthodontic treatment was established by using cone beam CT scanning technique and professional software.Analysis by ANSYS Workbench 15.0: 1.the maxillary second molars were anchorage,the traction arms were located in the mesial and distal of the canine,the length of the traction arms were 3,6 and 9mm respectively,observing the horizontal displacement trend of the maxillary teeth when the traction force was 150g;2.The mini-screw are implanted between the first and second molars and at a distance of 6mm from the top of the alveolar ridge,the traction arms were located in the mesial and distal of the canine,the length of the traction arms were3,6 and 9mm respectively,observing the horizontal displacement trend of the maxillary teeth when the traction force was 150g;Results:1.Establishment of a three-dimensional finite element model.The establishment of e-Brace brace,maxilla,tooth tissue,periodontal tissue,stainless steel wire and mini-screw,through the meshing,a total of 199974 units and 369212 nodes,with complete organization structure,high geometric similarity and mechanical structural similarities of the customized lingual orthodontic treatment of maxillary three-dimensional finite element model.2.During maxillary molars as anchorage closing space,different positions and lengths of traction arm effect maxillary dentition horizontal displacement.The traction arm located at the mesial of canine,it mainly happened arch width expansion form the distal of lateral incisor to the mesial of second premolar and arch width reductionfrom the distal of second premolar to the distal of second molar;When the traction arm located at the distal of canine,it mainly happened arch width expansion from canine to the mesial of first molar and arch width reduction from the distal of first molar to the distal of second molar;Both of them have the horizontal "bowing effect" mainly caused by tooth torsion.With the increase of traction arm length,the "bowing effect" becomes more obvious.3.During palatal mini-screw as anchorage closing space,different positions and lengths of traction arm effect maxillary dentition horizontal displacement.The traction arm located at the mesial of canine,it mainly happened arch width expansion in canine and from the distal of first molar to the distal of second molar,and arch width reduction from the mesial of second premolar to the mesial of first molar;With the increase of traction arm length,the increase of the arch width of the distal of canine obviously,and the trend of posterior teeth arch width expansion and posterior teeth arch width reduction are reducing.The clockwise torsion trend of anterior teeth was increased and the clockwise torsion trend of posterior teeth was decreased.The traction arm is located at the distal of canine and the traction arm length is 3mm,the arch width reduction from canine to the mesial of first molar and arch width expansion from the distal of first molar to the distal of second molar.Anterior teeth are counterclockwise torsion and posterior teeth are clockwise torsion;With the increase of traction arm length,the maxillary arch width increased as a whole,and the maxillary teeth are clockwise torsion increasing.From anterior to posterior,the trend of arch width expansion was more obviously.Conclusions:1.Three-dimensional images were scanned by cone-beam CT,combined with professional modeling software,a three-dimensional finite element model with complete tissue structure,high geometric similarity and similar mechanical structure was established,which can be used for the analysis of customized lingual orthodontic treatment for maxillary anterior teeth retraction.2.The molar anchorage is easy to cause the torsion-oriented horizontal “bowing effect”;The traction arm is located at the mesial of the canine,it happened arch width expansion from the distal of lateral incisor to the mesial of second premolar and arch width reduction from the distal of second premolar to the distal of second molar horizontal bowing effect;The tractionarm is located at the distal of the canine,it happened arch width expansion from the mesial of canine to the mesial of first molar and arch width reduction from the distal of first molar to the distal of second molar horizontal bowing effect;With the increase of traction arm length,horizontal “bowing effect” was more obviously.3.Palatal mini-screw anchorage are implanted between the first and second molars and at a distance of 6mm from the top of the alveolar ridge,the traction arm is located at the mesial of the canine,the horizontal "bowing effect" is no longer evident;The traction arm is located at the distal of canine and the traction arm length is 3mm,which basically eliminates the horizontal "bowing effect";...