Establishment Of Three-dimensional Finite Element Model Of Maxilla And Biomechanical Analysis Of Alveolar Bone Grafting In Patients With Unilateral Complete Cleft Lip And Palate

Objective:CBCT scans were performed to obtain DICOM data,which were imported into Mimics,Geomagic,Hypermesh,and Abaqus software to establish unilateral complete cleft lip and palate.The three-dimensional finite element model of the maxillary complex of UCLP patients was used to provide a theoretical model for the biomechanical analysis of the maxilla of UCLP patients.The model was used to study the biomechanical characteristics of maxillary cleft bone grafting under central occlusal force,and to provide biomechanical theoretical support for alveolar bone grafting.Methods:CBCT scans were performed on an 11-year-old UCLP patient in mixed dentition.The DICOM format data were imported into Mimics software to define the orientation,erase noise,and generate a 3D model.Then,a smooth,continuous and closed geometric model was generated by importing Geomagic software.Then,Hypermesh software was imported for meshing.Finally,Abaqus software was imported for finite element calculation and analysis to obtain the final three-dimensional finite element model.The finite element models were divided into four groups: total maxillary cleft group,total maxillary cleft group,upper 1/3 of the cleft group,and lower 1/3 of the cleft group.The material properties of the four groups of models were defined,the horizontal direction was set as the X axis,the sagittal direction was set as the Y axis,and the vertical direction was set as the Z axis,and the central bite force was applied.The stress and deformation nephograms of each group were output and analyzed.Result:1.The three-dimensional finite element models of the maxillary complex of UCLP patients,the three-dimensional finite element models of the whole cleft bone graft,the upper 1/3 of the cleft bone graft group,and the lower 1/3 of the cleft bone graft group were successfully established.On average,each model was divided into1082.3 million grids and 232.5 million nodes,which had good geometric similarity and biomechanical characteristics.2.There was no stress concentration area in the four groups of models,and the stress was large in the bilateral maxilla near the zygomatic bone.The stress distribution on both sides of the whole cleft was more uniform than that before bone grafting.The stress distribution of the lower 1/3 graft was more similar to that of the whole graft compared with the upper 1/3 graft.3.In the four groups of models,both sides of the fissure were displaced to the midline and upward and forward direction.In the whole cleft group,the narrowing of the cleft was more obvious,and the anterior-posterior and up-down displacements on both sides of the cleft were larger.The model results of the upper third group were similar to those of the whole group.Compared with the whole cleft group,the whole cleft group and the lower 1/3 of the cleft group had smaller narrowing of the cleft,and smaller displacement of the anterior and posterior parts.Conlution:1.Using CBCT scanning combined with Mimics,Geomagic,Hypermesh,and Abaqus modeling software,a three-dimensional finite element model of the maxillary complex of UCLP patients with good geometric similarity was successfully established,which can be used for biomechanical analysis.2.Under the central occlusal force,the stress cloud and deformation cloud of the lower 1/3 bone graft model were very close to the full maxillary cleft model.The stress and deformation clouds of the upper third of the cleft were similar to those of the whole maxillary cleft model.From the biomechanical point of view,the effect of total maxillary cleft bone grafting is the best,and the effect of alveolar bone grafting is very similar to that of total maxillary cleft bone grafting,and there is no substantial difference between them.3.Cleft bone grafting can bridge the two ends of the maxillary cleft and reduce the secondary biomechanical changes caused by the cleft deformity.4.Bone grafting from anterior nasal crest to nasopalatine foramen is of great biomechanical significance.It is necessary to ensure the effect of bone grafting in this area.