Collagen cross-linking and antibacterial enhancement in dental adhesives <i>via</i> lignin and lignin-capped silver nanoparticles fillers

The longevity of dental restorations is highly dependent on the durability of the resin-dentin interface, where collagen degradation and bacterial infiltration remain key challenges. Lignin, a natural and sustainable polymer, offers antioxidant, cross-linking, and antimicrobial potential, and its combination with silver nanoparticles (AgNPs) could further enhance antibacterial efficacy. This study aimed to investigate the use of lignin and lignin-capped AgNPs (lignin/AgNPs) as bio-based fillers in dental adhesives to improve collagen stability and antibacterial performance. Incorporating 0.5 wt% lignin and 0.5 wt% lignin/AgNPs into dental adhesives significantly improved bond strength, increasing from 15.36 MPa to 22.87 MPa and 27.54 MPa, respectively. FTIR analysis confirmed improved collagen cross-linking. While lignin alone provided limited antibacterial effects, lignin/AgNPs achieved strong activity against Streptococcus mutans. Importantly, both adhesives maintained bond strength after 6-month aging and exhibited no cytotoxicity at clinically relevant concentrations. These findings support their application in the development of advanced dental materials.