Antimicrobial effectiveness of oxidant and chelating agents combination in infected dentine: an ex vivo confocal laser scanning microscopy study

Abstract

Aim

To evaluate the intratubular antimicrobial activity of several oxidant and chelating agents associated or not with surfactants in experimentally infected root canals, using confocal laser scanning microscopy.

Methodology

Twenty-four dentine blocks from bovine incisors were contaminated for five days with Enterococcus faecalis (ATCC- 29212). Ten contaminated dentine specimens were irrigated for 5 min with 5.25% NaOCl followed by 17% EDTA for 2 min, and the other 10 with Hypoclean for 5 min followed by Tetraclean NA for 2 min. The remaining four specimens were used as positive and negative controls (2 samples each).Then, dentine blocks were stained with Live/Dead BacLight for analysis of the remaining live or dead bacteria using confocal laser scanning microscope. Comparison between and within groups was performed using the Mann Whitney test for independent samples and the Wilcoxon signed-rank test, respectively.

Results

After exposure to irrigants, the positive control group had a median of 67.41% of viable bacteria (95% CI: 48.15, 78.9) of viable bacteria, while NaOCl+EDTA group and Hypoclean+Tetraclean NA group had 3.77% (1.28, 15.92) and 0.87% (-0.42, 4.30) of viable bacteria, respectively. These results were significantly different each other, both overall and distinct by region (cervical and medium third), or depth (superficial and deep layer) (p<0.01 in all cases).

Conclusions

The use of adjunctive agents reducing the surface tension associated with oxidant and chelating agents improved the antimicrobial activity of irrigating solutions and intra-tubular decontamination against Enterococcus faecalis, possibly due to a better removal of the smear layer and deeper penetration into dentinal tubules.

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