Three-dimensional Finite Element Analyses Of The Deep Wedge-shaped Defective Premolars Restored With Different Methods

ObjectiveTo analyze the stress distribution in the deep wedge-shaped defective mandibular first premolars restored with different methods.Materials and MethodsThe three-dimensional finite element models of mandibular first premolar with deep wedge-shaped defect were created. The model which was untreated after root canal treatment served as control group. Then according to different treatment designs, 4 experimental groups were established as follows:resin filling (A), post restoration after resin filling (B), crown restoration after resin filling (C) and post and crown restoration after resin filling (D). Then 4 different post materials were chosen for establishing subgroup models:fiber post (B1,D1), AuPd post (B2, D2), pure Ti post(B3, D3), CoCr post(B4, D4). The force of 100 N was applied at 30°angle on the buccal inclined surface near the top of the buccal cusp. The maximum principal stress and Von Mises stress were investigated using the finite element analysis software.Results1. The maximum principal stress and Von Mises stress of the residual dentine were the same as those of the tip of defected region of the control group, and larger than those of the 10 experimental groups.2. For the models without crowns, the maximum principal stress and Von Mises stress of group A decreased much more than those in group B.3. Compared with group B, the maximum principal stress and Von Mises stress in residual dentine and the dentine of defected tip region and post-dentine surface of group C and D with crowns decreased obviously. Whether the residual dentine or the dentine of tip of the defected region, the maximum principal stress and Von Mises stress of the group C were similar to those of group D.4. With the increase of elastic modulus of the posts, the maximum principal stress and Von Mises stress of the post-dentine surface of the group B and D with cast metal post is larger than that in the model with fiber post.Conclusion1. On the condition of normal occlusal force, full crown restoration obviously improve the stress concentration of residual dentin.2. Post is not absolutely necessary and just filling with resin material followed by full crown restoration can be one of the alternative restorations. Compared with cast metal post, fiber post is more suitable.