Three-dimensional Finite Element Model Establishment Of Maxillary Sinus Pneumatization And Stress Analysis Of Maxillary Sinus Augmentation Of Bone Graft

ObjectiveA three-dimensional finite element model of maxillary sinus pneumatization was established to simulate the mechanism of maxillary sinus pneumatization and analyze the stress distribution of maxillary sinus pneumatization on different forms of maxillary sinus and bone graft after maxillary augmentation.Provide a theoretical basis for the choice of maxillary sinus lifting bone graft morphologyMethodsA total of 27 three-dimensional finite models of maxillary sinuses with or without sinus augmentation were constructed.According to the sinus floor anatomy in the mesiodistal direction,these models were divided into 3 groups:(i)the tapered group(tapered floor);(ii)the ovoid group(ovoid sinus floor);and(iii)the square group(square floor).In each group,sinus augmentation by different heights and widths was performed.The bone augmentation heights were 3,6and 9 mm.The bone floor augmentation widths were 8,10 and 12 mm.A diagnostic CBCT image of three patients was taken to generate the three-dimensional finite element models of the maxillary sinus.Spiral CBCT images of the maxillary sinus of each subject were collected in the original DICOM format of the data using i-CAT Vision software.Then,the data were imported into Mimics software for processing.Preliminary separation of the maxillary sinus from the surrounding tissue and establishment of a structural model using a mask.The STL files generated by Mimics were imported into Geomagic software and then adjusted,trimmed and modified again.3D finite element models were generated using SOLIDWORKS software.The geometry of the model was identified using the model of the maxillary sinus,cortical bone,cancellous bone,and maxillary sinus membrane 。 For mesh generation,all models were exported to ANSYS 17.0 software,a pressure of 100,500 and 1000 Pa was applied inside the maxillary sinus membrane to measure the stress on the bottom of the maxillary sinus and the bone graft.ResultIn the comparison of the three maxillary sinus prototype and bone graft stress,the square maxillary sinus has the largest von Mises stress on the entire surface of the bone graft model with the same bone graft height and width,and the top 1mm and base 1mm,while the ovoid and tapered maxillary sinus stress were similar.When the width of the ovoid maxillary sinus is 8mm and 12 mm,the peak value of von Mises stress on the whole surface of the bone graft model is the smallest when the bone graft height is 6mm,and when the width of the bone graft is 10 mm,the von Mises peak stress on the whole surface of the bone graft model decreases with the height of the bone graft.Both the tapered and square maxillary sinus bone graft stress decreased with the height of the bone graft.In the bone graft crest and base analysis,the von Mises peak stress of the bottom 1 mm at the base of each bone graft model was greater than that of the top 1 mm at the crestConclusionsBased on this experiment,the following conclusions can be drawn:1.The square maxillary sinus prototype and all bone graft models with the same height and width have a greater overall von Mises peak stress than tapered and ovoid maxillary sinuses,while tapered and ovoid maxillary sinuses are not much different.2.In the tapered and square different types of maxillary sinus,the stress on the overall surface of the bone graft model and the top 1mm and base 1mm are negatively correlated with the height of the bone graft.However,the overall surface stress of the ovoid maxillary sinus bone graft model decreases when the height of the bone graft increases from 3mm to 6mm,and the surface stress of the partial bone graft model increases when the height of the bone graft increases from 6mm to 9mm.What’s more,the stress on the overall surface of all bone graft models and the top 1mm and base 1mm has no obvious correlation with the bone graft width3.The three models of maxillary sinus bone grafting model have a larger reduction in von Mises peak stress when the height of bone graft increase from3 mm to 6mm,and a smaller decrease in von Mises peak stress when height of bone graft increase from 6mm to 9mm.Therefore,it is suggested that when the maxillary sinus augmentation,the height of the bone graft needs to be at least6 mm to effectively reduce the stress.4.The maximum von Mises stress on the overall surface of all bone graft models are concentrated at the base of the bone graft model,and in the layered stress analysis,the stress at the bottom of the base 1mm is much greater than the stress value at the top of the 1mm.Therefore,when the maxillary sinus is elevated,the range of maxillary sinus membrane dissection still needs to be increased to increase the width of the bone graft in order to compensate for the occurrence of bone resorption.