An Investigation of the Mechanical Characteristics of Four CAD-CAM Monolithic Zirconia Materials

Transparent CAD/CAM monolithic ceramics are increasingly used in dentistry due to their combination of high strength, esthetics, and durability, achieved through high yttria content and multilayered systems. This study evaluates the mechanical behavior of four widely used CAD/CAM ceramics, correlating their performance with microstructural characteristics. Bar-shaped specimens (n = 10 per material, for each test) of ZOLID® FX ML (ZF), IPS E.MAX® CAD (MC), E.MAX® ZIRCAD (ZM), and KAT-ANA® STML (KS) (all A2 shade) were prepared and sintered according to manufacturers’ protocols. Flexural strength and elastic modulus were measured using three-point bending, and Vickers hardness was determined separately. Statistical normality was confirmed with the Kolmogorov–Smirnov test. Flexural strength ranged from 252.8 ± 39.8 MPa (MC) to 547.6 ± 125.7 MPa (ZM), elastic modulus from 65.8 ± 6.5 GPa (MC) to 94.1 ± 5.8 GPa (KS), and hardness from 4.2 ± 0.2 GPa (MC) to 9.6 ± 0.6 GPa (ZF). High-elastic-modulus materials (KS, ZM) can better resist deformation under occlusal loads, improving long-term stability of posterior crowns, bridges, and implant-supported restorations. High hardness (ZF) provides superior wear resistance and preserves occlusal anatomy over time, making it suitable for thin-shell restorations and high-stress functional surfaces. Materials with lower modulus and hardness (MC) are more suitable for intra-coronal restorations or thin veneers where stress shielding and material compliance are advantageous. These findings support material selection based on mechanical demands, and further clinical studies are needed to confirm long-term performance.