Biomechanical behavior of endocrowns vs fiber post-core-crown vs cast post-core-crown for the restoration of maxillary central incisors with 1 mm and 2 mm ferrule height: A 3D static linear finite element analysis

To analyze the stress distribution of the maxillary central incisor with oblique fracture, repaired by different methods, using 3-dimensional finite element analysis. From the biomechanical point of view, it is expected to provide a reference for clinical selection of restoration method which is more conducive to stress distribution and preservation of dental tissue as much as possible. Use cone beam CT and finite element software to establish the finite element models of the maxillary central incisor with oblique fracture, and then create models according to 5 repairing methods(A. fiber post-core-crown group; B. cast post-core-crown group; C.3 mm deep endocrown; D.4 mm deep endocrown; E.5 mm deep endocrown)after root canal treatment, and analyze the Von Mises equivalent stress and maximum principal stress distribution and peak value of each model. When the height of dentin ferrule was fixed, the value of the Von Mises equivalent stress and the maximum principal stress in residual tooth tissue: group A was the highest, and there was no significant difference in group B, C, D and E. And the stress distribution area of 5 groups were the same. In prosthodontic layer: group B was the highest, while group A was the lowest, and the stress peak slightly increased with the increase of depth in group C, D and E. And the 5 groups were with the same stress distribution area as well. In adhesive layer: group A was the highest, while group B was the lowest, and there was little difference among group C, D and E. Group A was concentrated in 1/3 of the post tip, while group B,C,D and E were concentrated in 1/3 of the post and the post tips. Complete and high enough dentin ferrule is a requirement for repairing heavily defected maxillary central incisor with fiber post-core crown and cast post-core crown. When the dentin ferrule is incomplete, the stress distribution of the endocrown is more excellent than post-core-crown. And the endocrown with a depth of 3 mm retainer may be the best repair method. As for post-core crown restoration, the cast post-core crown is more favorable for the uniform distribution of residual tooth tissue than the fiber post-core crown.