Three-Dimensional Finite Element Analysis Of The Stress Distribution In Mandibular First Premolar Restored With Post-and-Core Crown

Objective:The aim of this study was to investigate the effect of incomplete ferrules on the stress distribution of mandibular first premolar restored with post and core crown using three-dimensional FEM,to evaluate stress distribution in remaining dentin,adhesive layer and within the post of premolar with different ferrule configurations.Methods:A standard mandibular first premolar was collected and scanned with CBCT,Mimics software was used for three-dimensional reconstruct,after processing with Geomagic Wrap,3D finite element models of the tooth restored with fiber post,resin core and ceramic crown were generated using Solidworks.Six groups were divided according to different ferrule designs:Group A(complete ferrule),Group B(buccal ferrule),Group C(lingual ferrule),Group D(mesial ferrule),Group E(distal ferrule)and Group F(no ferrule).Assembly and mesh generation were created by Abaqus.Under 45 degree oblique direction static loading of 200 N on the lingual surface of the buccal cusp,peak stress value and stress distribution pattern of Von Mises stress and max principal stress in the remaining dentin,adhesive layer and within the post were analyzed respectively.Results:1.For the complete ferrule group,peak VM stress in remaining dentin was observed 2mm below the crown margin on the buccal surface,the stress concentrated area on the buccal side was larger than that on the lingual side.Peak max principal stress and stress concentration were observed on the lingual surface of the root.2.Peak VM stress and max principal stress were observed in the apical area when no ferrule was present.Additional stress concentration was observed on the occlusal surface of the root.3.Peak VM stress was observed on the buccal surface of the root for the buccal and distal ferrule group,in the apical area for the mesial ferrule group and on the occlusal surface of the root for the lingual ferrule group.In all groups,peak max principal stress was observed on the lingual surface.In terms of peak stress value,the mesial ferrule model had highest VM stress value while the lingual ferrule model had the highest max principal stress value.4.For all groups,VM Stress in the adhesive layer mainly concentrated on the buccal side.Max principal stress concentrated on both the buccal and lingual side when ferrule is absence,while for other groups,it was mainly on the lingual side.The complete ferrule group presented lowest stress value.The buccal ferrule group showed similar stress distribution pattern with the complete ferrule group.The location of stress concentration changes when ferrule is absent.5.In terms of stress within the post,highest stress value was observed in the complete ferrule group,following by the no ferrule group.In all groups,peak VM stress and max principal stress all appeared in the apical third of the post.Peak stress values were lower in groups with incomplete ferrule.Conclusions:1.A complete,2mm ferrule is beneficial for stress distribution in remaining dentin and adhesive layer,with more stress transferred into the fiber post.A complete ferrule can increase fracture resistance and marginal seal.2.The absence of ferrule changes the stress distribution pattern in remaining dentin and adhesive layer,causing stress concentration.3.Stress distribution in remaining dentin and adhesive layer is nonuniform in the incomplete ferrule groups compared to the complete ferrule group,but better that in the no ferrule group.In the present study,the buccal ferrule group showed most favorable stress distribution in all the incomplete ferrule groups.4.Through the equipment,software and method of CBCT combined with 3D FEM,the model of post core and crown restoration system can be effectively established.The model is intuitive and accurate,similarity between groups and consistency of parameters are ensured to provide clinically significant results.Making it an efficient method for oral biomechanics research.