Effect Of The Height Of Ferrule And The Length Of Fiber Post On The Post-core Crown Restoration: Finite Element Analysis

Objective: Three-dimensional finite element method was used to analyze the stress of root and post adhesive,and to explore the biomechanical effects of different height of ferrule and length of fiber post on post-core crown restoration,as well as the relationship between the two factors influencing the outcome.Methods: The adult mandibular first premolars extracted by orthodontic treatment were scanned by micro-CT,and the files were imported into the image processing software of Mimics 21.0 in DICOM format,and then through a series of software such as geo-studio Magic 12.0,Siemens NX 12.0,the ferrule with height of0 mm,0.5 mm,1.0 mm and 1.5 mm was set up.The finite element models with fiber post length of 6 mm,8 mm and 10 mm were set up in 12 groups.In order to simulate the load of normal occlusion of the first mandibular premolars,the central fossa of the first mandibular premolars was located slightly to the buccal side,and the static loading direction was 100 N with a constant force of 45 ° to the long axis of the teeth.The distribution of the equivalent stress,the maximum principal stress and the peak stress of the tooth and the post adhesive were analyzed by ANSYS Finite Element Software.The biomechanical effects of different height of ferrule and length of fiber post on mandibular first premolars were discussed.Results: With the increase of the height of the ferrule or the length of the fiber post,the stress peak of the root decreased.When the length of fiber post was 6 mm and 8 mm,the root stress changed greatly in the group with ferrule height of 1.0mm-1.5 mm.The root stress value of 10 mm long fiber post was significantly affected by the height of ferrule 0 mm-0.5 mm group.When the height of ferrule was less than0.5 mm,the decrease of peak stress of the tooth was significantly increased with the increase of the length of fiber post.The height of ferrule 0.5 mm-1.0 mm group had little influence on the peak value of root stress of different fiber post length.The height of ferrule is between 0 mm and 1.0 mm,the overall decrease of root stress peak value of 10 mm long post is still the biggest.When the height of ferrule is more than 1.0 mm,with the increase of the length of fiber post,the decrease of the stress peak value of root first increases and then decreases,that is to say,the stress peak value of root with 8mm or 10 mm length of post approaches.Conclusion: 1.The increase of fiber post length can enhance the fracture resistance of the whole root.2.When the height of the ferrule is less than 1.0 mm,the length of fiber post should be increased as much as possible to increase the root fracture resistance under the premise of ensuring the sealing effect of the root tip3.When the height of the ferrule is greater than 1.0 mm,the fiber post that it is slightly larger than the length of the clinical crown can be applied.