OBJECTIVEThe objective of this paper is to analyze the stress distribution in the deep wedge-shaped defective mandibular first premolars restored with different methods.

METHODSThree-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 the control group. Then, according to different treatment designs, four 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). Four different post materials were then chosen for establishing the subgroup models: fiber post (B1, D1), AuPd post (B2, D2), pure Ti post (B3, D3), and CoCr post (B4, D4). A force of 100 N was applied at a 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 finite element analysis software.

RESULTS1) For the control group, the maximum principal stress and Von Mises stress of the residual dentine were the same as those of the tip of the defect. 2) Compared with the control group, the maximum principal stress and Von Mises stress of groups A, B, C, and D decreased greatly (P<0.05). The maximum principal stress and Von Mises stress of groups C and D with crowns were similar. The maximum principal stress and Von Mises stress of the post-dentine surface of groups B and D with fiber post were less than those in the cast metal post models (P<0.05). 3) The displacement of the buccal cusp of group A was similar to that of the control group (P>0.05) and larger than those in groups B, C, and D (P<0.05).

CONCLUSIONSIt is necessary for deep wedge-shaped defective teeth to be treated with full crowns, but a post is not necessary. If a post is used, fiber post with elastic modulus closer to the dentine is more suitable than metal post.
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