Characterization of an Ex Vivo Model for the Assessment of Root Canal Disinfection

Electrospun Nanofiber Films Suppress Inflammation In Vitro and Eradicate Endodontic Bacterial Infection in an E. faecalis-Infected Ex Vivo Human Tooth Culture Model

Treatment failure of endodontic infections and their concurrent inflammations is commonly associated with microbial persistence and reinfection, also stemming from the anatomical restrictions of the root canal system. Aiming to address the shortcomings of current treatment options, a fast-disintegrating nanofibrous film was developed for the intracanal coadministration of an antimicrobial (ZnO nanoparticles) and an anti-inflammatory (ketoprofen) agent. The electrospun films were fabricated based on polymers that dissolve rapidly to constitute the actives readily available at the site of action, aiming to eliminate both microbial infection and inflammation. The anti-inflammatory potency of the nanofiber films was assessed in an in vitro model of lipopolysaccharide (LPS)-stimulated RAW 264.7 cells after confirming their biocompatibility in the same cell line. The nanofiber films were found effective against Enterococcus faecalis, one of the most prominent pathogens inside the root canal space, both in vitro and ex vivo using a human tooth model experimentally infected with E. faecalis. The physical properties and antibacterial and anti-inflammatory potency of the proposed electrospun nanofiber films constitute a promising therapeutic module in the endodontic therapy of nonvital infected teeth. All manuscripts must be accompanied by an abstract. The abstract should briefly state the problem or purpose of the research, indicate the theoretical or experimental plan used, summarize the principal findings, and point out major conclusions.

Antimicrobial Effect of Peptide DJK-5 Used Alone or Mixed with EDTA on Mono- and Multispecies Biofilms in Dentin Canals

INTRODUCTION

The present study aimed to evaluate the antibacterial effect of a new peptide, DJK-5, used alone or mixed together with EDTA on mono- and multispecies biofilms in dentin canals covered by a smear layer with or without preceding sodium hypochlorite (NaOCl) irrigation.

METHODS

One hundred twelve dentin blocks (224 final specimens) were prepared and divided into 56 groups, and Enterococcus faecalis or multispecies bacteria were introduced into dentinal tubules by centrifugation. After 1 week of cultivation, a uniform smear layer was created on the surface of the dentin blocks, and the samples were exposed to sterile water, 17% EDTA, 2% or 6% NaOCl, 10 μg/mL DJK-5, or a mixture of 8.5% EDTA +10 μg/mL DJK-5 or were combined treated with the solution in the following sequence: 2% or 6% NaOCl +10 μg/mL DJK-5, 2% or 6% NaOCl + 8.5% EDTA +10 μg/mL DJK-5, 2% or 6% NaOCl + 8.5% EDTA + 10 μg/mL DJK-5. Specimens without a smear layer treated by 6% NaOCl or 10 μg/mL DJK-5 served as the positive control. The irrigant exposure time was 3 or 10 minutes. The antibacterial efficacy was determined by live/dead staining and confocal laser scanning microscopy.

RESULTS

The smear layer reduced the antibacterial capacity of 6% NaOCl and 10 μg/mL DJK-5. The efficacy of 2% or 6% NaOCl followed by 10 μg/mL DJK-5 was superior to 10 μg/mL DJK-5 alone (P < .05) but inferior to 2% or 6% NaOCl + 8.5% EDTA + 10 μg/mL DJK-5 and 2% or 6% NaOCl + 8.5% EDTA + 10 μg/mL DJK-5 (P < .05). The mixture of 8.5% EDTA and 10 μg/mL DJK-5 had the same disinfection effectiveness as 10 μg/mL DJK-5 used alone (P < .05). Using 2% or 6% NaOCl before EDTA + peptide always resulted in the highest killing (P < .05).

CONCLUSIONS

The smear layer inhibits the disinfectant effect in dentin. Peptide DJK-5 showed a strong antibacterial effect against mono- and multispecies biofilms in dentin canals. The highest killing was measured when 6% NaOCl was followed by a mixture of EDTA and peptide DJK-5.

Antibacterial efficacy of a human β-defensin-3 peptide on multispecies biofilms

INTRODUCTION

The aggregation of mixed bacterial flora into sessile biofilms on root canal surfaces can be one of the causes of persistent apical periodontitis. The aim of this study was to evaluate the antibacterial efficacy of human β-defensin-3 (HBD3) peptide on multispecies biofilms by using confocal laser scanning microscopy.

METHODS

Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans, and Enterococcus faecalis were cultured in a peptone-yeast-glucose broth, and their culture suspensions were combined in equal proportions. The mixed bacteria were inoculated on sterile coverslips placed into the wells of tissue culture plates to permit the formation of mixed species biofilm. After incubation for 3 weeks, the samples were treated for 24 hours with saline (control), saturated calcium hydroxide solution (CH), 2% chlorhexidine solution (CHX), and 50 μg/mL HBD3 solution. A commercial biofilm/viability assay kit was used to assess cell viability and analyze the 3-dimensional architecture of biofilms. The percentage of dead cells was determined from the ratio of biovolumes for the red subpopulation and the total biofilm.

RESULTS

Three medication groups showed a significant reduction of biovolume within the biofilms compared with the control group (P < .001). The HBD3-treated biofilms had a higher percentage of dead cells than the other medication groups (P < .05). The CH and CHX groups showed higher levels of bactericidal activity than saline (P < .05), and there was no significant difference between the 2 groups (P > .05).

CONCLUSIONS

HBD3 peptide exhibited more antibacterial activity against mature multispecies biofilms in vitro than either CH or CHX.