Merlon machinability and mechanical properties of four CAD/CAM block materials

The mechanical properties and machinability of CAD/CAM materials are critical in determining their clinical applications. This study evaluated and compared the mechanical behavior and machinability of three composite-based blocks: Cerasmart (CS), Lava Ultimate (LU), and Grandio Blocs (GR), with a ceramic-based block, Initial LRF (IR). Flexural strength, flexural modulus, fracture toughness, and Vickers hardness were assessed following standardized ISO protocols. The machinability was tested using the Merlon fracture method (ISO 18675:2022), and machined margins were examined using scanning electron microscopy (SEM). One-way ANOVA was performed for statistical analysis (α = 0.05). GR exhibited the highest flexural strength among the tested materials, while IR showed significantly higher flexural modulus and Vickers hardness than the other materials. CS showed the lowest fracture toughness values. SEM observations revealed clear differences in surface quality after machining, with the ceramic block IR displaying inferior edge integrity compared with the composite-based blocks. All four materials demonstrated satisfactory machinability according to ISO standards. However, composite-based blocks exhibited better edge quality compared with the leucite-reinforced ceramic block. The findings indicate that composite-based restorative materials may result in better adaptation at the dental margins in posterior restorations, whereas ceramic materials present greater hardness, making them particularly suitable for enamel replacement.