Three-Dimensional Finite Element Analysis On En Mass Intrusion And Retraction Of Maxillary Anterior Teeth With J-Hook Headgear

Objective: To study the biomechanical mechanisms of En mass intrusion and retraction of maxillary anterior teeth with J-hook headgear by three-dimensional finite element analysis. Methods: We established the three-dimensional finite element model by ANSYS 17.1 software and divided the model into two groups (A and B) according to the different location on which the force was applied: Group A, the force was applied mesial to lateral incisor; Group B, the force was applied distal to lateral incisor. The two groups were simulated En mass intrusion and retraction of maxillary anterior teeth with J-hook headgear. The force direction was maintained at 30 degrees to the sagittal plane and 20 degrees to 60 degrees to the occlusal plane, which was changed every 5 degrees. The applied force was maintained at 1.5 N. Then the displacement of maxillary anterior teeth and periodontium stress distribution were analyzed. Results: The displacement of maxillary anterior teeth was the clockwise and lingual movement with intrusion. With the increase of the traction angle, the displacement became overall retraction and intrusion, and finally the displacement became the counter-clockwise rotation with the labial movement with intrusion. And as the force was applied at 35 degrees (A) and 45 degrees (B), the maxillary anterior teeth showed a relatively uniform overall intrusion and retraction without rotation. Conclusions: For maxillary anterior teeth with normal lip inclination, placement of J-hook headgear mesial to lateral incisor is more conducive to the overall intrusion and retraction of maxillary anterior teeth. In addition, the traction angle should be adjusted according to individual conditions and treatment goals.