Evaluation Study on the Addition of Nano-Hydroxyapatite-Silica into Glass Ionomer Cement

Introduction: Glass ionomer cements are used for many clinical applications in dentistry due to their self-adhesive, anti-caries, and good biocompatibility properties. Despite the advantages, their main disadvantage is that it has low strength. Objective: To evaluate and compare material characterisation, surface hardness, compressive strength, and flexural strength of material following the addition of nano-hydroxyapatite-silica into conventional glass ionomer cement (GIC) matrix. Methodology: Nano-hydroxyapatite-silica was synthesised using one-pot sol-gel with different concentration of tetraethyl orthosilicate (TEOS). It was then characterised using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). GIC specimens were fabricated according to the instructions from manufacturer. Nano-hydroxyapatite-silica was added at different percentages of weight. Reinforced GIC specimens were stored for 24 hours in distilled water at 37°C. Surface hardness, and compressive and flexural strength of the conventional and nano-HA-Si-GIC were evaluated. The mechanical properties results were analysed using one-way ANOVA and Tukey's test. The level of significance was set at P0.05 Results: FTIR and XRD analysis confirmed the formation of hydroxyapatite-silica nano-particles. SEM and TEM images showed all hydroxyapatite crystals were elongated and covered by smaller silica particles. The nano-powder consisted of a mixture of spherical silica particles (50 nm) and elongated hydroxyapatite particles in the range between 100-200 nm. The hardness, compressive strength, and flexural strength of nano-HA-35SiO2-GIC was statistically higher than nano-HA-21SiO2-GIC and nano-HA-11SiO2-GIC. The highest values for hardness (64.77 6.18), compressive strength (143.42 13.94 MPa) and flexural strength (17.68 1.81 MPa) were recorded upon the addition of 10% nano-HA-35SiO2 to GIC, an increase of ∼36%, ∼19.7%, and ∼53.34% respectively as compared to conventional GIC. Conclusions: The addition of nano HA-silica to conventional GIC significantly enhanced the mechanical properties of the material. Hence, it can be suggested as a potential dental restorative material in dentistry. Keywords: Glass ionomer cement, nano-Si, nano-HA, adhesive dentistry, biomaterials