Glass-Ceramic Fillers Based on Zinc Oxide-Silica Systems for Dental Composite Resins: Effect on Mechanical Properties

The potential of glass ceramics as applicable materials in various fields including fillers for dental restorations is our guide to present a new procedure for improvements of the mechanical properties of dental composites. This work aims to use Zn₂SiO₄ and SiO₂-ZnO nano-materials as fillers to improve the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Zn₂SiO₄ and SiO₂-ZnO samples were prepared and characterized by using XRD, FE-SEM, EDX, and FT-IR techniques. The XRD pattern of the SiO₂-ZnO sample shows that ZnO crystallized in a hexagonal phase, while the SiO₂ phase was amorphous. Similarly, the Zn₂SiO₄ sample crystallized in a rhombohedral crystal system. The prepared samples were used as fillers for the improvement of the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Five samples of dental composites composed of Bis-GMA/TEGDMA mixed resins were filled with 2, 5, 8, 10, and 15 wt% of SiO₂-ZnO, and similarly, five samples were filled with Zn₂SiO₄ samples (2, 5, 8, 10, and 15 wt%). All of the 10 samples (A-A) were characterized by using different techniques including FT-IR, FE-SEM, EDX, and TGA analyses. According to the TGA analysis, all samples were thermally stable up to 200 °C, and the thermal stability increased with the filler percent. Next, the mechanical properties of the samples including the flexural strength (FS), flexural modulus (FM), diameter tensile strength (DTS), and compressive strength (CS) were investigated. The obtained results revealed that the samples filled with 8 wt% of SiO₂-ZnO and 10 wt% of Zn₂SiO₄ had higher FS values of 123.4 and 136.6 MPa, respectively. Moreover, 8 wt% of both fillers displayed higher values of the FM, DTS, and CS parameters. These values were 8.6 GPa, 34.2 MPa, and 183.8 MPa for SiO₂-ZnO and 11.3 GPa, 41.2 MPa, and 190.5 MPa for the Zn₂SiO₄ filler. Inexpensive silica-based materials enhance polymeric mechanics. Silica-metal oxide nanocomposites improve dental composite properties effectively.