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Abstract

Objectives: This study aimed to evaluate the impact of incorporating zinc oxide nanoparticles (ZnO-NPs) and ruthenium II complex (Ru) as photosensitizers (PSs) on the chemo-physical properties and antimicrobial photodynamic therapy (aPDT) potential of an experimental dental resin. Methods and Materials: Different concentrations of Ru (0, 0.28, or 0.56 wt%) and ZnO-NPs (0 or 10 wt%) were added into an experimental dental resin (DR), resulting in six groups. The degree of conversion (DC) was evaluated (n=5), followed by flexural strength (FS) and flexural modules (FM) tests at 24-hour and 4 mos (n=12). Antimicrobial and photocatalytic potential were assessed under dark and blue-LED irradiation (81 J/cm²) against a dual-species biofilm model of Streptococcus mutans (S. mutans) and Candida albicans (C. albicans), immediately and after 4 mos aging (n=9). Data were statistically analyzed (ANOVA/Tukey tests; p<0.05). Results: All groups with PSs showed similar or increased DC compared to the control. Groups containing Ru alone and the 10%ZnO+0.28%Ru group had a statistically significant DC increase. At 24-hour storage, there was no significant difference in FS between groups. After 4 months, FS values increased significantly across all formulations, though they were significantly lower than the control in all groups except 0.28% Ru. The highest concentrations (10% ZnO + 0.56% Ru) resulted in the lowest FS values. After 4 months, 10% ZnO showed significantly higher FM compared to the control. After 24 hr, ZnO showed significant antibacterial effects against S. mutans in dark conditions. All groups showed reduced CFU for both species when light-treated compared to dark control, except for 10% ZnO group against C. albicans. After 4 months, significant CFU reductions were observed in groups containing PSs treated with light compared to the dark control, highlighting sustained antimicrobial properties with PS and light treatment. Conclusion: The study demonstrated that combinations of ZnO and Ru could sustain the aPDT effect and indicated that the effects on mechanical stability varied depending on the formulation, with some concentrations leading to a reduction in FS values while others showed improvements in FM over time.