Effectiveness of zinc-oxide nanoparticles compared to NaOCl/EDTA treatment in eliminating Enterococcus faecalis from infected root canals

The purpose of this study was to test the antimicrobial properties of zinc-oxide nanoparticles (ZnO-NP) against Enterococcus faecalis that have penetrated into dentinal tubules. An in vitro root canal model was prepared from eighty extracted single-rooted human teeth that were instrumented and inoculated with two E. faecalis strains: OG1RF, producing the collagen binding protein, Ace, and TX5256, deficient in Ace. The negative control group was left uninoculated. After 21 days of incubation at 37°C in a moist chamber, the teeth were irrigated with sterile saline (positive control group), NaOCl/EDTA, or ZnO-NP then sectioned longitudinally and into 1-2 mm slices from the middle and coronal areas of the tooth. The slices were stained with SYTO9 and propidium iodide (PI) and bacteria were assessed through confocal laser scanning microscopy (CLSM).;RESULTS: Real-Time PCR performed on paper point samples showed that irrigation with NaOCl killed significantly more bacteria in the root canal than ZnO-NP (p<0.05). Measurements CLSM pixel intensity of SYTO9 demonstrated that ZnO-NP were significantly more efficient at killing E. faecalis in the dentinal tubules than saline or NaOCl (P<0.05).;CONCLUSION: This preliminary study shows that ZnO-NP could be useful as an endodontic irrigant to kill bacteria in dentinal tubules.