Investigating the antibacterial activity of Thyme Oil/TiO2 modified resins against oral pathogenic bacteria

Abstract

Dental composites lack inherent antimicrobial activity, leading to secondary caries and restoration failure. This study developed a novel thyme oil/TiO2 nanoparticle filler to impart sustainable antibacterial functions to dental resins. TiO2 nanoparticles were synthesized via a sol-gel method and characterized as 20–30 nm crystalline anatase particles. Functionalization with thyme oil was confirmed by FTIR, with 5.8% thyme oil content measured by TGA. Resin disks containing 0.5–2 wt% thyme-TiO2 exhibited significant inhibition zones against S. mutans, L. acidophilus and C. albicans (8–12 mm) compared to thyme oil-free controls (0 mm) (p < 0.05). Thyme-TiO2 at 1–2 wt% showed sustained release of thyme oil over 15 days with bacterial viability reduction of 68–99% compared to unmodified resin (p < 0.05). Resin-dentin microtensile bond strengths were 45–50 MPa for 0.5–2 wt% thyme-TiO2 and not significantly different from control (p > 0.05). Likewise, flexural strength, elastic modulus and surface microhardness values were unchanged with thyme-TiO2 incorporation ≤ 2 wt% (p > 0.05). DPSC viability was > 90% for all resins, indicating good cytocompatibility. Overall, the thyme-TiO2 nanocomposite successfully endowed the dental resin with potent, long-lasting antibacterial effects without compromising key mechanical properties.