Antibiofilm efficacy of ε-polylysine hydrochloride against Enterococcus faecalis biofilms and its biocompatibility: A promising root canal medicament.

Abstract

Objectives: Enterococcus faecalis (E. faecalis) is a predominant pathogen associated with refractory apical periodontitis (RAP), owing to its strong biofilm-forming ability and alkali resistance, which may compromise the antimicrobial efficacy of conventional calcium hydroxide (Ca(OH)₂)-based intracanal medication. This study aimed to evaluate the antibacterial and antibiofilm effects of ε-polylysine hydrochloride (ε-PLH) against E. faecalis within the root canal microenvironment, as well as its cytocompatibility, effects on dentin microhardness, removability, and potential to promote periapical healing.

Methods: The antibacterial activity of ε-PLH against E. faecalis was evaluated by determining the minimum inhibitory concentration (MIC) and assessing its ability to disrupt preformed E. faecalis biofilms. In vitro cytocompatibility was examined using cell viability assays after exposure to different concentrations of ε-PLH. An ε-PLH-based paste was then formulated using propylene glycol (PG) as the vehicle. The effects of intracanal application on dentin microhardness and material removability were evaluated using extracted human root segments. In vivo antibacterial efficacy and periapical healing were further assessed in a rat model of infected root canal established by intracanal inoculation of E. faecalis, followed by treatment with different intracanal medicaments. Normality and homogeneity of variance were assessed before statistical analysis, and comparisons among groups were performed using one-way analysis of variance (ANOVA) followed by appropriate multiple comparisons tests.

Results: The MIC of ε-PLH against E. faecalis was 125 mg/L. At a concentration of 4 MIC, ε-PLH significantly disrupted preformed biofilms, outperforming Ca(OH)₂ (P < 0.05), while maintaining high cytocompatibility. The ε-PLH-PG paste did not adversely affect dentin microhardness after intracanal application for up to 14 days and was more easily removed than Ca(OH)₂. In vivo, ε-PLH exhibited greater antibacterial efficacy and promoted better periapical healing compared to Ca(OH)₂ (P < 0.05).

Significance: ε-PLH combines sustained antibiofilm efficacy, low cytotoxicity, easy removability, and minimal influence on dentin microhardness, highlighting its strong potential as a clinically applicable intracanal disinfectant for root canal therapy.