Chelating and antibacterial properties of chitosan nanoparticles on dentin

Abstract

Objectives: The use of chitosan nanoparticles (CNPs) in endodontics is of interest due to their antibiofilm properties. This study was to investigate the ability of bioactive CNPs to remove the smear layer and inhibit bacterial recolonization on dentin.

Materials and methods: One hundred bovine dentin sections were divided into five groups (n = 20 per group) according to the treatment. The irrigating solutions used were 2.5% sodium hypochlorite (NaOCl) for 20 min, 17% ethylenediaminetetraacetic acid (EDTA) for 3 min and 1.29 mg/mL CNPs for 3 min. The samples were irrigated with either distilled water (control), NaOCl, NaOCl-EDTA, NaOCl-EDTA-CNPs or NaOCl-CNPs. After the treatment, half of the samples (n = 50) were used to assess the chelating effect of the solutions using portable scanning electronic microscopy, while the other half (n = 50) were infected intra-orally to examine the post-treatment bacterial biofilm forming capacity. The biovolume and cellular viability of the biofilms were analysed under confocal laser scanning microscopy. The Kappa test was performed for examiner calibration, and the non-parametric Kruskal-Wallis and Dunn tests (p < 0.05) were used for comparisons among the groups.

Results: The smear layer was significantly reduced in all of the groups except the control and NaOCl groups (p < 0.05). The CNPs-treated samples were able to resist biofilm formation significantly better than other treatment groups (p < 0.05).

Conclusions: CNPs could be used as a final irrigant during root canal treatment with the dual benefit of removing the smear layer and inhibiting bacterial recolonization on root dentin.

Keywords: Biofilm; Chitosan; Dentin; Nanoparticles; Recolonization.

Figure 1. Representative images from the portable scanning electron microscope (×500) and confocal laser scanning microscope (×40). The irrigated pre-infection samples can be seen in images (a) - (e), and the infected samples after experimental irrigation protocols can be seen in images (f) - (j). A substantial amount of smear layer was observed when the samples were irrigated with sterile distilled water (a) and NaOCl (b). Visible dentinal tubules were seen in the samples treated with NaOCl-EDTA (c), NaOCl-EDTA-CNPs (d) and NaOCl-CNPs (e). A positive cellular viability and evident biomass were observed in the control (f), NaOCl (g) and NaOCl-EDTA (h) groups. The NaOCl-EDTA-CNPs and NaOCl-CNPs groups had decreased biomass (i) and interfered with bacterial growth (j). All bars represent 20 µm.

Figure 2. The percentage of areas with open dentinal tubules for each score (1 to 4). Having less than 10% of the area containing open dentinal tubules was scored as one, having 10 - 50% of the area containing open dentinal tubules was scored as two, having 50 - 70% of the area containing open dentinal tubules was scored as three and having more than 70% of the area containing open dentinal tubules was scored as four.

^*Different letters within a column depict a significant difference (p < 0.05). NaOCl, Sodium hypochlorite; NaOCl-EDTA, Sodium hypochlorite-ethylenediaminetetraacetic acid; NaOCl-EDTA-CNPs, Sodium hypochloriteethylenediaminetetraacetic acid-chitosan nanoparticles; NaOCl-CNPs, Sodium hypochlorite-chitosan nanoparticles.