Computational Evaluation of Stress Distribution in Endocrown-Restored Immature Mandibular Molars: A Finite Element Approach

A three-dimensional finite element analysis (FEA) was performed to evaluate stress accumulation and distribution in endodontically treated immature and mature mandibular molars restored with endocrowns. Three tooth models representing different stages of root development (Cvek 2, Cvek 3, and mature) were generated from cone-beam computed tomography data. Endocrowns were fabricated using lithium disilicate (LDS) and resin nanoceramic (RNC). In immature teeth, two apexification strategies were simulated: a 3 mm mineral trioxide aggregate (MTA) apical plug followed by gutta-percha obturation, and complete canal obturation with MTA. All models were subjected to axial (600 N) and oblique (200 N) loading. A total of 20 finite element models were analysed. Endocrown material and loading direction were the main factors affecting von Mises stress distribution, whereas root development stage and apexification technique showed limited influence. LDS resulted in reduced stress transmission to the residual dentin, despite higher stress accumulation within the restoration itself. In the LDS groups, von Mises stress values in the root dentin ranged from 35.24 to 35.96 MPa under oblique and from 42.93 to 44.45 MPa under axial loading, while the RNC group exhibited higher values (39.36–40.40 MPa and 51.59–53.66 MPa, respectively). These findings indicate that endocrown restoration after apexification is a reliable treatment option for immature mandibular molars with extensive structural loss, with LDS demonstrating more favorable biomechanical behavior.