Unveiled stress dynamics: the role of post length and repair materials in perforated tooth models: a finite element analysis study.

Background: Post placement is a common practice to reinforce weakened roots. However, the choice of post length and repair material for root perforation influences the stress distribution within the dentin and surrounding tissues. This study aimed to evaluate the effects of post length and repair materials on the stress distribution in perforated tooth models through finite element analysis (FEA).

Methods: A three-dimensional FEA model of a mandibular first molar tooth was created via Materialise 3-Matic software. Posts with lengths of 4 mm, 6 mm, and 8 mm inside the root and perforation areas in the middle third of the distal root were created. The control groups (CGs) included nonperforated models (CG4: Control group treated with 4 mm post, CG6: Control group treated with 6 mm post, CG8: Control group treated with 8 mm post) and those with unrepaired (UR) perforations (P) (P4/UR, P6/UR, P8/UR). MTA or Biodentine were used as repair materials for the main analysis groups (P4/MTA, P6/MTA, P8/MTA, P4/Biodentine, P6/Biodentine, P8/Biodentine); subsequently, all the models were restored with a ceramic crown. A 100 N force was applied through opposing teeth, and the maximum von Mises stress values and stress distributions in the model were analyzed.

Results: The maximum von Mises stress values in P4/MTA, P6/MTA, P8/MTA, P4/Biodentine, P6/Biodentine, P8/Biodentine models were slightly lower than those in P4/UR, P6/UR, P8/UR models. In the perforated models, extending the post from 6 mm to 8 mm reduced the stresses in the dentin and the post, while increasing the stresses in the perforation area. P8/UR model had the highest stress value at 63.22 MPa, followed by P8/MTA (62.80 MPa) and P8/Biodentine (36.20 MPa), and the lowest stress value was in P6/Biodentine (15.92 MPa) in the perforation area. The lowest stress accumulation was observed in P8/Biodentine (0.036 MPa) model in the PDL.

Conclusions: In perforated models, although the overall stresses in the dentine reduced with longer posts, the stresses in the perforation area increased. Biodentine enhances the mechanical stability of tooth structures and reduces stress concentrations, making it a suitable material for managing perforated teeth in post-endodontic restorations.