Three-dimensional Finite Element Stress Analysis Of Inlay Restoration Of Mandibular First Molar With Different Undercut Sizes

ObjectiveThrough the three-dimensional finite element analysis method,this paper studied the effects of different sizes of undercuts and filling materials on the biomechanical behavior of tooth tissue,bonding layer and prosthesis after restoration of the weak tooth tissue of the right mandibular first molar with Class I cavity,in order to provide a theoretical basis for clinical Class I cavity retention and inlay restoration.Methods1.CBCT scans the isolated teeth of the right mandibular first molar,obtains the three-dimensional data of the right mandibular first molar,and exports it in DICOM format.2.Import the collected DICOM data into mimics21.0 for 3D reconstruction and export the STL format model.3.Import the enamel,dentin and pulp cavity in STL format exported by mimics21.0 software into Geomagic Studio 2019 software,reverse geometry,generate 3D geometric models,and export them to x one by one_T format.4.Using Unigraphics NX 10 software to establish a three-dimensional finite element model of the pulpy all-ceramic inlay restoration of the Class Ⅰ hole of the right mandibular first molar,which was divided into two groups according to the concave height,namely,2.0mm and 2.5mm;According to the depth of undercut,they are divided into three groups:1,2 and 3,which are 0.5mm,1.0mm and 1.5mm respectively;According to the filling material,it is divided into two groups,a and b,which are glass ion Fuji IX GP and composite resin Filtek Z350 XT;Group A0 of control group:the shaft wall is not inverted,the bottom is flat and the wall is straight,and the hole depth is 2.0mm.In control group B0,the shaft wall is not inverted,the bottom is flat and the wall is straight,and the hole depth is 2.5mm.Load 300N vertically and diagonally on the occlusal surface,record the stress data and analyze the stress distribution.Results1.The effect of composite resin and glass ion as cavity filling materials on the equivalent stress peak value and maximum principal stress value of tooth tissue,prosthesis and bonding layer is close.2.The stress distribution,equivalent stress peak value and maximum principal stress value of each part of B1 group and control group are close.Conclusion1.The mandibular first molar model established in this study has realistic morphology,geometric similarity,and repeatability.2.In terms of filling materials,glass ions and resins can be considered as filling materials for concave surfaces,and the difference in stress distribution is not significant.3.Based on the stress analysis of various parts,the tooth tissue and restoration have the best resistance when the remaining concave depth is 0.5mm and the concave height is 2.5mm after the preparation of Class I holes.4.When repairing Class I holes,increasing the bonding area appropriately is beneficial for reducing the stress of the adhesive layer.