Antibacterial Effects of Silica Nanoparticles Loading Nano-silver and Chlorhexidine in Root Canals Infected by Enterococcus faecalis.

Introduction: The persistence of microbial infection can lead to endodontic failure. Enterococcus faecalis (E. faecalis) is acknowledged to be a closely associated bacterium. This study investigated the antimicrobial effects of mesoporous silica nanoparticles (nMS) carrying nano-silver and chlorhexidine (nMS-nAg-Chx) on E. faecalis.

Methods: Analyses were conducted to assess the antimicrobial efficacy of nMS-nAg-Chx towards planktonic E. faecalis, including the zone of inhibition, minimal inhibitory concentration (MIC), and growth curves. The measurement of lactic acid, scanning electron microscopy (SEM), live-dead bacteria staining, and quantitative real-time PCR (qRT-PCR) were done to further investigate its anti-biofilm effect. Colony forming unit (CFU) and SEM were used to assess its efficacy in infected root canals.

Results: The growth of planktonic E. faecalis was suppressed with a MIC value of 25 μg/mL (P＜0.05). nMS-nAg-Chx concentration-dependently inhibited biofilm formation of E. faecalis with the reduction of lactic acid (P < 0.05), sparse biofilm structure, reduced percentage of viable bacteria (P < 0.05), and suppressed expression of ebpR, gelE, ace, and efa genes (P < 0.05). The seven-day sealing of nMS-nAg-Chx resulted in a notable reduction in bacterial counts compared to the saline control group in the E. faecalis infected root canals (P < 0.05).

Conclusion: NMS-nAg-Chx effectively inhibits E. faecalis and removes its biofilm from infected human root canals. It may be used for endodontic treatments in the control of E. faecalis bacteria as an intracanal medication.