Influence Of Cavity Design And Restorative Material Type On Stress Distribution In Maxillary Premolars:A Finite Element Analysis

AimThe objective of this study was to investigate the effects of cavity design and material type on the stress distribution of the maxillary first premolar restored with inlays,which would provide a theoretical basis for the selection of indications and materials of inlay.Methods1.A finite element model of the maxillary first premolar was established.The three dimensional data of the maxillary first premolar was obtained from CBCT.The images obtained were input into 3D modeling softwares Mimics,Geomagic Studio 2012 and Solidworks.After a great trail of operations,the 3D geometric model of maxillary first premolar differentiating enamel,dentin,pulp,together with periodontal ligament and alveolar bone surrounding it was generated.Then the software Hypermesh was used to built the 3D finite element model.Ultimately,the 3D finite element model is verified in the software Abaqus with mechanical parameters assigned and 200N force at two directions(parallel to the long axis or 45 degree to the long axis lingually)loaded.2.Based on the 3D finite element model of the maxillary first premolar,three kinds of cavities(O,MO,MOD)were designed,then each type of cavity was restored with CAD/CAM inlay made of different materials including resin,glass ceramic and lithium silicate ceramic.All models were input into Hypermesh in which the models call be meshed automatically.Then,200N force was loaded at two directions(parallel to the long axis or 45 degree to the long axis lingually)respectively,the corresponding peak von Mises stress and the von Mises stress distribution mode of the restored maxillary first premolars were studied.Results1.A three dimensional finite element model of the maxillary first premolar differentiating enamel,dentin,pulp,together with periodontal ligament and alveolar bone surrounding it was generated.The model has favorable geometric and mechanical similarity.2.When different cavities were restored with inlays made of the same material,the larger the cavity,the higher the von Mises stress concentration under both loading conditions,and the stress concentration area closer to mesial root cervix.3.When the same cavity were restored with inlays made of different materials,the larger the elastic modulus of the restorative material,the lower the von Mises stress concentration of enamel,and the higher the von Mises stress concentration of dentin under two loading conditions.Conclution1.CBCT scanning technology,digital image processing engeneering and finite element method can be applied synthetically to establish a precise three dimensional finite element model of the maxillary first premolar,which lay the foundation for further research.2.The von Mises stress distribution of the dental cervix was greatly affected by the marginal ridge,and the completeness of marginal ridge has a positive effect on reducing the risk of dental fracture.3.Considering the reduction of fracture risk,it is suggested that the composite resin with approximate elastic modulus of dentin be chosen as inlay restorative material.