Establishment Of Three-Dimensional Finite Element Model And Biomechanical Study On Maxillary Protraction Of The Maxilla Of The Patient With Cleft Lip And Palate

Cleft lip and palate is the most common oral and maxillofacial congenital abnormalities.Ravage and scar aider repairing operation,and abnormal occlusion mechanism result in obstacle of maxillary bone growth and the defect in appearance and function.As to the orthodontic treatment,an early protraction technique may usually be used to induce the growth of maxillary bone.Recently,the biomechanics studies in this field are seldom reported.This study has explored a faster method for establishing finite element model of maxilla of the patient with the cleft lip and palate.This model has been used to study the effect of different direction of protraction,simulating reparation of maxillary fissures expanding treatment,and the change rule of maxillary stress,strain and shift so as to supply the basic scientific data for clinical treatment.The study includes two parts:PartⅠ:Establishment of 3-dimensional finite element model of maxilla of the patient with the Complete unilateral cleft lip and palate with spiral CT scanningObjective:To explore a faster and more precise method for establishing 3-dimensional(3 D)finite element model of maxilla of the patient with the complete unilateral cleft lip and palate.Methods:The surface of model was created by using Mimics software to deal with Dicom standard files obtained by scanning the cranium of the patient with multi-slices helical CT.Then,the 3D finite element model for complete unilateral cleft lip and plate in maxillary was established by Ansys software.Results:A 3D finite element model of maxilla of the patient with complete unilateral cleft lip and palate was constructed with 27405 units and 26876 nodes.Conclusion:The combination of Mimics(Materialists Interactive Medical Image Control System)software,Geomagic studio software, Ansys software,and spiral CT is able to create 3D finite element counter mode,which provided a fast and valid method to study complete unilateral cleft lip and palate.PartⅡ:The study on three-dimensional finite element model of maxillary protraction of the maxilla of the patient with cleft lip and palateObjective:To study the effective rule of protraction in different direction,simulating reparation of maxillary fissures and expanding on stress,strain and shift of maxillary bone,so as to supply the scientific data for treatment of the maxilla of the patient with cleft lip and palate.Methods:Based on the establishment of three-dimensional finite element model of maxilla with cleft lip and palate,this study applied ANSYS 10.0 software to simulate protraction,expanding and repairing fissures of maxillary bone,then we analyzed the change of maxillary stress and shift on the same force of traction in different direction.Results:1,With 500g/per lateral protraction and the protraction angle between 20-45°,the shape of maxillary plate bow showed internal shrinkage.There was an obvious correlation between internal shrinkage and direction of protraction.The more small of angle between direction of protraction and functional occlusion plane,the more large of internal shrinkage of teeth bow.The more large of angle between direction of protraction and functional occlusion plane,the more small of internal shrinkage of teeth bow.2,With 500g/per lateral protraction and protraction angle 30°for simulating maxillary expanding,the normal lateral bow had no internal shrinkage as well as the abnormal one.3,With 500g/per lateral protraction and protraction angle 30°for simulating reparation of maxillary fissures,the unrepaired maxillary fissures expanded,however,the first main and von Mises stress of simulating repaired craniofacial compound enlarged in local stress spots, but other areas were even.Conclusions:1,With protraction,maxillary palate showed internal shrinkage. There was an obvious correlation between direction of protraction and internal shrinkage range.2,The more small of angle between direction of protraction and functional occlusion plane,the more large of internal shrinkage of teeth bow;The more large of angle between direction of protraction and functional occlusion plane,the more small of internal shrinkage of teeth bow;Maxillary expanding could improve the shrinkage of maxillary bow treated by protraction obviously.3,Combining application of maxillary expanding with protraction treatment in patients with cleft lip and palate was more liable to improve the development of maxillary bone.4,The maxillary fissures could enlarge by protraction without reparation;The first main and yon Mises stress of craniofacial bone distribute evenly under protraction after fissures repaired.5,The protraction treatment was more important to develop maxillary bone after repairing maxillary fissures.