BACKGROUND: Clinically, dentin ferrule has great influence on resistance, retention and edge sealing of post-core crowns.
OBJECTIVE: To analyze the stress distribution of a three-dimensional post-crown model with labial and lingual oblique defects of the maxillary central incisor by finite element analysis.
METHODS: A standard maxillary central incisor was selected and scanned by cone beam CT, and then, scanning data were imported to Mimics17 software. The CAD and UG software were used to construct the post-crown model with labial and lingual oblique defects. The dentin ferrule height of the defective side was designed to be 0 mm, and according to the dentin ferrule height at labial side-the dentin ferrule height at lingual side, there were the following groups: 0 mm- 0 mm, 0 mm-0.5 mm, 0 mm-1.0 mm, 0 mm-1.5 mm, 0 mm-2.0 mm, 0.5 mm-0 mm, 1.0 mm-0 mm, 1.5 mm-0 mm, 2.0 mm-0 mm, 0.5 mm-0.5mm, 1.0 mm-1.0 mm, 1.5 mm-1.5 mm, 2.0 mm-2.0 mm). In the crown cut 1/3, 1/3 at the junction, the Von Mises stress distribution of the root dentin and fiber post was analyzed by finite element analysis using a force of 100 N at 45° to the long axis of the tooth
RESULTS AND CONCLUSION: (1) Root dentin stress distribution: In the case that the dentin ferrule at both labial and lingual sides was complete, with the increasing of the dentin height, the root Von Mises stress from the focus on the neck gradually became more evenly distributed and the peak stress gradually decreased. In the case of defective dentin ferrule, the peak of the Von Mises stress which had the dentin ferrule at the lingual side or the labial side was lower than that without the dentin ferrule, but at the same height, the dentin ferrule’s stress reduction at the lingual side was more obvious, close to the dentin ferrule ferrule complete group. (2) Fiber post stress distribution: in the case that the dentin ferrule at both labial and lingual sides was complete, with the increasing of the dentin height, fiber post’s Von Mises stress was gradually reduced. In the case of defective dentin ferrule, fiber post’s Von Mises stress which had dentin ferrule at the labial or lingual side was lower than that without the dentin ferrule, but at the same height, the dentin ferrule’s stress reduction at the labial side was more obvious. Overall, the lingual ferrule is more obvious on reducing root stress concentration than the labial ferrule, and the lingual ferrule height is beneficial to enhancing tooth resistance; the labial ferrule is more obvious on reducing the peak stress of fiber post and luting cement than the lingual ferrule, and the labial ferrule height is beneficial to increasing the retention and stabilization of the fiber post-core crown, and the effect becomes more obvious with at least 0.5-1.0 mm labial ferrule.