The suitability of different FEA models for studying root fractures caused by wedge effect

Area of Science:

• Biomaterials Science
• Dental Mechanics
• Computational Engineering

Background:

• Vertical root fractures are a concern following post-endodontic treatment.
• The "wedge effect" from post intrusion is a proposed mechanism.
• Finite element analysis (FEA) is used to study these stresses, but model simplifications require validation.

Purpose of the Study:

• To evaluate the accuracy of simplified 2D finite element analysis (FEA) models in simulating stresses related to the "wedge effect".
• To determine if specific FEA model configurations can adequately represent the tendency for vertical root fracture.

Main Methods:

• Three plane strain (PS) and two axisymmetric (Axi) FEA models of the root's apical third were created.
• Models varied in representation of gutta-percha and dentin-post bonding (bonded vs. non-bonded).
• A 165 N longitudinal load was applied, and maximum principal stress (sigma max) was analyzed.

Main Results:

• Stress magnitudes and orientations varied significantly across different models.
• The axisymmetric non-bonded (Axi-nB) model was the only one where all maximum principal stress vectors were perpendicular to the root plane, indicating fracture tendency.
• Adhesion between the post and dentin substantially reduced maximum principal stress.

Conclusions:

• The axisymmetric non-bonded (Axi-nB) FEA model is suitable for analyzing stresses leading to vertical root fracture via the "wedge effect".
• Plane strain models and the bonded axisymmetric model do not accurately represent the stress orientation for vertical root fracture due to the wedge effect.
• Model simplification requires careful consideration to ensure accurate simulation of biomechanical phenomena in endodontically treated teeth.