Finite element analysis for fracture resistance of reattached human tooth fragment with different types of retentive preparation techniques

Objective: Restoration of traumatized incisors by reattachment of the original tooth fragment appears to be the most conservative treatment approach. But the measurement of forces acting on natural tooth in-vivo poses many challenges. The advent of finite element analysis (FEA) has made it possible to demonstrate the propagation of stress through each part of a tooth and its restoration. The objective of this study was to evaluate and compare the fracture resistance of reattached human tooth fragment with different types of retentive preparation techniques using finite element analysis.

Study design: An intact maxillary central incisor was obtained, scanned by laser and its Computer Assisted Device (CAD) model was generated and then converted to Finite Element Model(FEM). Mechanical properties of tooth specimen and materials were added on the generated mesh. These reattached fragments were then fractured with a force applied at 30°, 45°, 70° and 90° to the long axis of tooth. FEA Calculation was run with the setup.

Results: The highest fracture strength recovery was found with internal dentinal groove (64.97%) followed by labial double chamfer with lingual over-contour (54.49%), subsequently by labial and lingual double chamfer (51.31%) and least was with simple reattachment (28.27%).

Conclusions: Fracture resistance varied with different retentive techniques and greatest strength was offered by internal dentinal groove preparation.