Green-Synthesized TiO₂ Nanoparticles Improve Mechanical Performance of Glass Ionomer Cements

Glass ionomer cements (GICs) are widely used in restorative and luting dentistry due to their fluoride release and chemical adhesion to dental tissues; however, their limited mechanical strength necessitates reinforcement strategies. The objective of this study was to investigate the effects of hemp-derived, green-synthesized titanium dioxide (TiO₂) nanoparticles on the surface and mechanical properties of two commercially available GICs with different clinical indications. TiO₂ nanoparticles were synthesized using Cannabis sativa leaf extract via a biogenic reduction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), confirming anatase-phase crystallinity, spherical morphology, and nanoscale particle size (28-49 nm). The nanoparticles were incorporated into Ketac™ Molar Easymix (restorative) and Ketac™ Cem Radiopaque (luting) GICs at 1%, 3%, and 5% (w/w), with nanoparticle-free formulations serving as controls (n = 10). Surface roughness, Vickers microhardness, and flexural strength were evaluated. Surface roughness increased in a concentration-dependent manner in both materials, with the highest values observed at 5% TiO₂ incorporation. In Ketac™ Molar Easymix, 1% and 3% TiO₂ significantly enhanced flexural strength and microhardness, whereas 5% resulted in reduced performance, consistent with SEM-observed nanoparticle agglomeration. In contrast, Ketac™ Cem Radiopaque exhibited no significant changes in flexural strength, although maximum microhardness values were recorded at 1% TiO₂ concentration. These findings demonstrate that low concentrations of hemp-derived TiO₂ nanoparticles can effectively reinforce restorative GICs and highlight the potential of green nanotechnology as a sustainable approach for improving dental biomaterials.