Effects of sustainable bamboo-derived cellulose nanocrystals on the mechanical performance and antibacterial potential of dental resin composites

Dental resin composites require improved durability and resistance to bacterial colonization, while sustainable and biocompatible fillers remain desirable. This study developed dental resin composites incorporating bamboo-derived cellulose nanocrystals (CNCs) and evaluated their mechanical and antibacterial potential. CNCs were extracted from bamboo powder through sequential alkaline and oxidative treatments followed by acid hydrolysis and dialysis. The rod-like CNCs were incorporated at 0, 1.5, and 3 wt% into a UDMA/TetraEGDMA resin matrix containing 50 wt% Sr-SiO₂ glass fillers. Morphology and structure were characterized by SEM, TEM, and FTIR. Degree of conversion (DC), microhardness, flexural strength, flexural modulus, and antibacterial potential against Staphylococcus aureus (S. aureus) were assessed. The extracted CNCs showed rod-like morphology. DC values (49-51%), microhardness, and flexural strength did not differ significantly among the groups. The 3 wt% group showed a significantly higher flexural modulus (p < 0.05). The 1.5 wt% group demonstrated the lowest recoverable CFU counts (p < 0.0001), suggesting preliminary antibacterial potential. Bamboo-derived CNCs enabled loading-dependent modulation for dental resin composites, with 3 wt% improving the flexural modulus without compromising overall mechanical performance, whereas 1.5 wt% yielded the lowest recoverable CFU count. These findings indicate that CNCs act as multifunctional nanofillers rather than conventional fillers, providing a sustainable strategy to enhance dental resin composites.