Construction Of Finite Element Model Of Alveolar Cleft In Dog And Relative Biomechanical Research

Purpose:(1) To explore a method to construct a finite element model (FEM) of alveolar cleft in dogwith sutures that can provide reliable theoretical basis for related animal experiments andclinical guidance for treatment plans in post-graft patients.(2) To explore a proper selection of the loaded value by comparing the changes of stressand displacement in graft area and median palatine suture by loading different values ofexpansion forces on the same teeth of the constructed model.(3) To explore a proper selection of the loaded teeth by comparing the changes of stressand displacement in graft area and median palatine suture by loading the same value ofexpansion force on different teeth on the constructed model.Methods:(1) An initial geometric model was constructed using MIMICS to segment teeth,periodontal ligaments and bones and to simulate the alveolar cleft and bone graft withDICOM obtained by scanning the skull of beagle with spiral-CT. Geomagic Studio wasused to construct the solid model of sutures, and to smoothen and optimize the entiremodel. With Femap an FEM of alveolar cleft in dog with sutures was constructed byendowing the corresponding material parameters and creating the3-D FEM mesh. Wetested and verified the model to confirm the accuracy and effectiveness of it. (2) Four different values of expansion forces(5MPa,10MPa,20MPa,30MPa) were loadedon bilateral canines, which were divided into four groups (G1-G4) to simulate theexpansion of dental arch in clinical treatment.(3) The same value of expansion force(10MPa) was loaded on bilateral canines (G5),bilateral fourth premolars (G6) and bilateral canines and fourth premolars (G7), the threegroups of loaded teeth, which simulated the expansion of dental arch in clinical treatment.The changes of stress and displacement in graft area and median palatine suture werecompared.Results:(1) A3-D FEM of alveolar cleft dog was constructed with3939729units and805570nodes, which included teeth, periodontal ligaments, bones, bone graft and sutures. Thevalidation results were similar to the pre-experimental results.(2) After simulated loading, the graft areas in four groups were subjected to the expansionforce which increased with load value. The displacements of canines of cleft side weremuch greater than the health side in G3and G4, in which the bilateral asymmetricdisplacements were too large. The displacements of bilateral canines were similar, but thetensile stress on graft area and median palatine suture was small in G1. The displacementof canine of cleft side was slightly greater than the health side in G2, and the graft areaand the entire median palatine suture were subjected to great tensile stress.(3) After simulated loading, the graft areas in three groups were subjected to the expansionforce which was transferred from the distal to the mesial. The graft area and the entiremedian palatine suture were both subjected to tensile stress in G5and G7. The tensilestress was less on the graft area and the middle part of median palatine suture in G6, in which the front part of median palatine suture even presented compressive stress. Thedisplacements of canines and fourth premolars of health side were greater than the cleftside in G6and G7. The graft area and the entire median palatine suture were bothsubjected to tensile stress, and the displacement of canine of cleft side was slightly greaterthan the health side only in G5.Conclusions:(1) The FEM constructed by spiral-CT, MIMICS, Geomagic Studio and Femap is accurateand has favorable geometric similarity and the similarity of the material and can be usedfor biomechanical analysis.(2) According to the analysis when canines were loaded with an expansion force of10MPa, the graft area and the entire median palatine suture were both subjected to tensilestress and the displacements of bilateral canines were similar. We recommend selecting10MPa as the value of expansion force in animal experiments.(3) According to the analysis when canines were loaded with the expansion force, the graftarea and the entire median palatine suture were both subjected to tensile stress, thedisplacement of canine of cleft side was slightly greater than the health side. Besides sinceit is much easier for clinical operation to place the expansion device on canines due totheir shape and location, we recommend selecting canines as the teeth being loaded inanimal experiments.