Mechanical behavior of esthetic CAD/CAM post–core restorations: a 3D finite element analysis

This study aims to investigate the fracture resistance of CAD/CAM post-core restorations manufactured from different materials and to evaluate stress distribution using finite element analysis (FEA). Root canal treatment was performed on 48 single-rooted mandibular second premolars, which were randomly assigned to four groups (n = 12). The experimental groups were as follows: Group PEEK (polyether ether ketone), Group Nano-hb (nanohybrid composite), Group GFR-C (glass fiber-reinforced composite), and Group Zir (zirconia). Post–core restorations were fabricated using a CAD/CAM system. Following thermocycling, the specimens were subjected to static loading in a universal testing machine. For finite element analysis, a mandibular second premolar model was constructed, and a load of 100 N was applied at a 45° angle to the long axis. The maximum von Mises stresses were recorded. Fracture resistance values were statistically analyzed using one-way ANOVA, and post hoc pairwise comparisons were performed with the Dunnett T-test. Fracture resistance was highest in Group Zir (1240.20 N), followed by GFR-C (993.53 N), with PEEK (674.07 N) and Nano hb (666.10 N) showing significantly lower values (p < 0.05). FEA showed the highest stress concentration in the zirconia post-core (69.230 MPa), while the lowest was in PEEK (22.968 MPa). However, root stress was highest in PEEK (40.390 MPa) and lowest in zirconia (17.773 MPa). Zirconia and GFR-C groups showed a higher incidence of catastrophic fractures, whereas PEEK and Nano hb exhibited mostly favorable fracture patterns. Finite element analysis and examination of fracture types have shown that rigid zirconia post-core restorations cause severe fractures due to their mechanical properties. In contrast, materials with an elasticity modulus similar to that of dentin provide a more physiological stress distribution and result in minor fractures.