Three-dimensional Finite Element Analysis Of Maxillary Protraction Assisted By Palatal Bone-supporting Expander

[Objective] A three-dimensional finite element model of the craniofacial complex was established to analyze the influence of the difference between the anterior traction directions and the shape of t palatal bone-supporting expander on the displacement trend of the craniofacial complex and the stress distribution of the craniofacial suture when the palatal bone-supporting expander assists the maxillary anterior traction.Provide effective theoretical basis for clinical application.[Methods] A 12-year-old male volunteer with underdeveloped maxillary Class III malocclusion was selected,CBCT scan was used to obtain the original data,and Mimics,Geomagic Studio,Unigraphics NX and other reverse engineering software were used to establish 3 types(L1,L2,L3)A three-dimensional finite element model of maxillary protraction assisted by palatal bone-supporting expander.Use the Ansys workbench software to set the open 0.25 mm at the spiral arch expander of the palate,simulating the rapid palate expansion force in the clinic,and apply a 500 g force to the traction hooks on both sides of the device,and the direction is respectively aligned with the maxillary occlusal plane,It is 0 °,15 °,30 °,45 ° in front and down.Select three landmark points of craniofacial complex,namely N point(Nasion),IOB point(Infraorbital point),A point(Subspinale).Measure the displacement value of the selected marker points in three dimensions and the stress value of each bone suture,and draw the table,line chart,stress distribution and displacement cloud of the craniofacial complex.Finally,analyze,summarize and summarize the results.[Results] We established 3 types three-dimensional finite element model of maxillary protraction assisted by palatal bone-supporting expander,which including skull,maxillary dentition,periodontal ligament,and device.At the same traction angle,there is no statistical difference in the three-dimensional displacements of the three points of the N points(Nasion),IOB point(Infraorbital point),and A point(Subspinale)in L1,L2,and L3;With the increase of the traction angle,the displacement values of the N,IOB,and A points in the Z direction decrease linearly;As the traction angle increases,the absolute value of the displacement of points A and N in the Y axis decreases linearly,and the absolute value of the displacement of IOB in the Y axis increases linearly;In the three groups L1,L2 and L3,the same traction force has different stress values on the same bone suture;The same traction force produces different stresses in each bone suture,and the stress changes of each bone suture with the increase of the traction angle.[Conclusions] When maxillary zygomatic bone supported forward traction combined with expansion,the three device forms have little effect on the displacement trend of the craniofacial,which can cause the craniofacial to move forward with counterclockwise rotation,but L2 Relatively low stress on the same bone gap,with the increase of the traction angle,the counterclockwise rotation of the craniofacial decreases,and the stress of each bone suture changes differently.In the clinical application of the zygomatic bone support device for forward traction,a smaller traction angle can be selected for patients with deeper occlusion and deeper coverage,on the contrary,for patients with shallow occlusion and shallower coverage Large traction angle.