Mechanical Properties of Custom-Made Post and Core Made of CAD/CAM Dental Ceramics

Abstract

Objective: This study aimed to evaluate and compare the fracture resistance, failure modes, surface morphology, and crystallographic properties of three CAD/CAM fabricated post and core materials zirconia, resin nano ceramic, and experimental barium-based mica glass ceramic against a 3D-printed resin post and core used as a control. Materials and Methods: Sixty custom-designed post and core specimens (n = 15 per group) were fabricated and cemented into standardised resin tooth analogues. Four groups were tested: Group one - zirconia posts (CAD/CAM milled), Group two - resin nano ceramic posts (CAD/CAM milled), Group three - glass mica ceramic posts (CAD/CAM milled), and Group four - 3D-printed resin posts (control). All samples underwent static compressive loading until failure. Fracture resistance values were recorded and analysed using one-way ANOVA with post hoc Holm-Sidak comparisons (α = 0.05; power = 1.000). Failure modes were categorised under stereomicroscopy. Scanning electron microscopy (SEM) was performed to assess surface morphology and fracture patterns, and X-ray diffraction (XRD) was used to characterise the crystallographic structure of each material. Results: Zirconia exhibited the highest mean fracture resistance (1031.48 ± 150.40 N), but failed in a catastrophic, non-restorable manner. Resin nano ceramic (344.31 ± 71.21 N) and barium-based mica glass ceramic (377.29 ± 82.42 N) showed moderate strength and favourable, restorable failure modes, with SEM indicating energy dissipation through microcracking and crack deflection. The 3D-printed resin group showed the lowest fracture resistance (222.81 ± 10.87 N). SEM revealed distinct microstructural features for each material, while XRD confirmed the presence of densely packed polycrystalline zirconia and lamellar mica crystallites in the novel ceramic group. Conclusion: Material selection for post and core restorations should be based not only on fracture resistance but also on failure mode, microstructural behaviour, and retrievability. While zirconia offers superior strength, resin nano ceramic and the experimental mica-based ceramic demonstrate more favourable and restorable failure characteristics. Further research is recommended to investigate long-term fatigue resistance, modulus of elasticity via flexural testing, and performance in simulated clinical environments.