Biomechanical behavior of various post-and-core systems in severely compromised mandibular molars: A 3D finite element analysis

Abstract

Statement of problem

Selecting a post-and-core system for endodontically treated posterior teeth remains challenging. Cast post-and-core (CPC) and fiber post with composite resin core (FPCC) systems are used to restore structurally compromised teeth. Their biomechanical interactions with the remaining tooth structure under functional loading remain poorly understood.

Purpose

The purpose of this finite element analysis study was to assess how CPC and FPCC restorations influence internal stresses and interfacial stress distributions in a restored mandibular first molar under functional loading.

Material and methods

A fully dentate mandibular model (W10532; 3B Scientific GmbH) was reconstructed using microcomputed tomography (TomoScope H; Werth Inc). A mandibular first molar was restored with a CPC or an FPCC, each supporting a complete coverage monolithic lithium disilicate crown. Finite element analysis simulated occlusal loading during masticatory function using physiologic loading vectors and validated boundary conditions. Anatomically accurate geometries and anisotropic material definitions were incorporated. The models were meshed with a converged finite element grid (<0.2%). Maximum principal stress was evaluated in enamel, dentin, bone, and periodontal ligament, while von Mises stress quantified internal post-and-core behavior. Stress and strain distributions were compared among restorations, with emphasis on internal post stresses and interfacial tensile stresses at the crown–core–post junction.

Results

The CPC model exhibited a 234% increase in internal post stresses compared to the FPCC model. Dentin stress levels remained similar between the systems, varying by about 4%. The FPCC model demonstrated a 15.2% increase in tensile stress at the crown–core–post interface and a 63.8% increase along the apical crown margin. These elevated interfacial stresses coincided with micromovement at bonded interfaces.

Conclusions

Based on the findings of this finite element analysis study, CPC restorations concentrate higher internal stresses. In contrast, FPCC restorations reduce internal post stress but increase interfacial tensile stresses. Dentin stresses remained consistent across systems, indicating that the main difference is in failure mode.