Finite Element Analysis Of Different Restoration Methods For Mandibular First Molars With Different Defect Types

ObjectiveTo analyze the stress magnitude and distribution of different defect types in mandibular first molars restored with different kinds of restoration.Methods1.Mandibular first molar model small area defect on the occlusal surface and corresponding restorations(inlay,crown,fiber crown,horizontal endocrown and obliques endocrown)were established by the reverse engineering technique and finite element method.A static load force of 225N was applied vertically and diagonally to the occlusal surface of dental crown to simulate the normal occlusion.The maximum von Mises stress of various parts in tooth and restorations under different loads were recorded.2.Mandibular first molar models with large area defect on the adjacent-occlusal surface and corresponding restorations(fiber crown and endocrown)were established by the reverse engineering technique and finite element method.A static load force of 225N was applied vertically and diagonally to the occlusal surface of dental crown to simulate the normal occlusion.The maximum von Mises stress of various parts in tooth and restorations under different loads were recorded.3.Mandibular first molar models with different adjacent defect height and corresponding endocrowns were established by the reverse engineering technique and finite element method.A static load force of 225N was applied vertically and diagonally to the occlusal surface of dental crown to simulate the normal occlusion.The maximum von Mises stress of various parts in tooth and restorations under different loads were recorded.Results1.The tooth stress distribution of the inlayed group was different under the two loadings,but the rest groups were similar under the two loads.The EQV stress peak values of tooth and restorations at oblique loading were significantly higher than those of vertical loading.Under two load conditions,the maximum EQV stress of tooth in the inlay group was the highest,and the two crown groups was higher than that of the two kinds of endocrown groups;the maximum of EQV stress of restorations in the inlay group was the smallest,and the two crown groups was lower than that of the two kinds of endocrown groups.2.Under two kinds of load,the EQVstress distribution of the teeth in groups of fiber post reinforced crown and endocrown were both concentrated in the neck of the tooth.The peak EQV stress of the teeth in fiber post reinforced crown group was higher than that in endocrown group.The EQV stress of restoration in fiber post reinforced crown group focused on the edge of the crown,which in endocrown group focused on the adhesive surface of the medullary cavity.The peak of equivalent stress of restoration in endocrown group was higher than that in fiber post reinforced crown group.3.The EQV stress distribution of the residual tooth tissue and the endocrown was similar in different groups.The maximum EQV stress of the residual tooth tissue and the endocrown increased with the the decrease of the residual height.ConclusionEndocrown can effectively reduce the stress of dental tissue and reduce the possibility of crown fracture.