Three-dimensional Finite Element Analysis Of Four Materials For Mandibular First Molar Inlay Restorations

Objective In this experiment,Three-dimensional finite element model of Inlay and Onlay restoration of mandibular first molar with mesial occlusal distal(MOD)cavity type was used to select polyetheretherketone and its composite materials and other traditional restorative materials for restoration,to analyze the stress level and stress distribution of the teeth under different loading methods,and to find out the influence of Inlay and Onlay restoration of different materials on the change of stress in the remaining tissue,to providing a reference basis for more reasonable selection of materials and restoration methods in clinical practice.Methods Cone Beam Computer Tomography(CBCT)was used to scan the object,and the CBCT image containing the mandibular first molar was selected and imported into Mimics Research 19.0,and then the finite element model of the tooth was established by Geomagic Wrap 2017,UG NX 12.0.The MOD defect cavity was prepared on this basis and restored with Inlays and Onlays covering all the cusps;the mesh was divided and assigned through the finite element software Abaqus 6.14 to simulate a static load with a force value of 200 N and a direction of vertical loading and 45° oblique loading;the Von Mises was selected as the analysis index,PEEK,CFR-PEEK,Composite resin,and Emax as the restoration,the Von Mises stress and stress distribution clouds of restorations of mandibular first molars were used for analyze the effects of different materials and restorative methods on the stress changes in the remaining tissues.Results 1.The Von Mises stress of each group was greater under oblique loading conditions than under vertical loading for each of the four restorations.2.When the same material was applied,the stress level of the Onlay group was smaller than that of the Inlay group under both loading conditions;the stress distribution of the Onlay group was smaller than that of the Inlay group under both loading conditions,and the stress distribution was more uniform with no obvious concentration areas.3.The stress level of the four materials is close to each other,but as the elasticity modulus of the material increases,the stress is gradually distributed in the gingival wall,pulp wall and buccal pulp line angle.Conclusions 1.The influence of oblique loading conditions on the tissues of teeth is more significant,and the cusp slope should be minimized clinically to avoid the harm caused by unfavorable lateral forces.2.Of the two restorative methods,the application of Onlays can effectively reduce the stress and make the stress distribution more uniform,which has a significant advantage in resisting lateral forces.Under the conditions set in this experiment,Onlay restorations are a safer and more reasonable choice.3.Restorative materials with too high elasticity modulus may increase the instability within the dentin,and as the elasticity modulus of the material decreases,it helps to reduce the chance of fracture of the dentin layer,however,low elasticity modulus may cause stress concentration in the enamel.In order to achieve a more uniform distribution of stress,inlay restorative materials with a elasticity modulus close to that of dentin should be choosed.4.The application of PEEK for restoration of tissue defects may increase the stress in enamel layer;CFR-PEEK is a more uniform distribution of restorative materials for restoration of tissue defects in the dentin.However,the long term effects need to be observed through clinical trials.