Biosynthesized TiO₂ Nanoparticles to Enhance the Mechanical and Antibacterial Properties of Type-II Glass Ionomer Cement for Dental Restorative Applications

Titanium dioxide (TiO₂) and its nanoforms are highly valued in dentistry for their biocompatibility, antimicrobial effects, and photocatalytic properties, making them useful functional additives in restorative materials. In this study, TiO₂ nanoparticles (TiO₂ NPs) were synthesized using bio-assisted methods and incorporated into type-II glass ionomer cement (GIC) to investigate their effect on the mechanical and antimicrobial performance of the cement. The modified GICs were evaluated for setting time, compressive strength, antimicrobial activity against <i>Streptococcus mutans</i> and <i>Lactobacillus acidophilus</i>, and antioxidant potential. The study explores whether incorporating bio-assisted TiO₂ NPs can enhance the functional and therapeutic properties of conventional GICs. TiO₂ NPs were synthesized using <i>Piper betle</i> aqueous extract and <i>Ocimum sanctum</i> hydroalcoholic extract using hydrothermal and microwave-assisted synthesis methods, respectively. Synthesized TiO₂ NPs were subsequently subjected to physicochemical characterization and in vitro hemolysis and cytotoxicity assessments. Further, TiO₂ NPs were incorporated into type-II GIC powder to formulate four modified cement groups (F2-F5), along with an unmodified control group (F1), at two nanoparticle weight ratios. Compressive strength was measured using a universal testing machine (UTM) at a crosshead speed of 0.5 mm/min until the samples fractured. Antimicrobial activity was determined by exposing GIC discs (5 × 2 mm) to <i>S. mutans</i> (Microbial Type Culture Collection (MTCC) 890) and <i>L. acidophilus</i> (MTCC 10307) cultures, followed by plating and colony counting after incubation at 37°C for 24 and 72 hours. The antioxidant activity of F1-F5 formulations was also evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. A significant reduction in the setting time was observed in GIC formulations containing 100 mg/g of TiO₂ NPs regardless of the synthesis method, with the difference in mean setting time between the control and TiO₂-incorporated groups being statistically significant (p < 0.05). Incorporation of 100 mg/g TiO₂ NPs also resulted in a notable increase in compressive strength (F3: 290 ± 11 MPa; F5: 301 ± 12 MPa), whereas the 50 mg/g formulations did not show statistically significant improvement. Antimicrobial evaluation revealed that even the control GIC exhibited low colony counts (<300) with no apparent increase after 72 hours; however, the addition of TiO₂ NPs provided a modest enhancement in antibacterial effects at both 24- and 72-hour timelines. TiO₂ NPs showed less than 20% antioxidant activity, likely due to residual phytoconstituents as indicated by Fourier transform infrared (FTIR) analysis. Formulations F3 and F5 displayed slightly higher antioxidant activity than the pure GIC (still <10%), although the differences were not considerable at the tested concentrations. Overall, the results of our research indicate that plant-mediated synthesis resulted in TiO₂ NPs with favorable morphology, enhanced antibacterial effects, and good cytocompatibility. When incorporated into type-II GIC, TiO₂ NPs contributed to both increased compressive strength and decreased setting time. The TiO₂ NP-modified GICs also exhibited a slight improvement in antimicrobial activity and mild antioxidant effects, indicating their potential suitability as restorative materials after elaborate research on other required mechanical properties and pilot clinical performance.