Comparison of Three Endodontic Irrigant Regimens against Dual-Species Interkingdom Biofilms: Considerations for Maintaining the Status Quo

Abstract

Endodontic infections are often interkingdom biofilms, though current clinical management rarely considers this phenomenon. This study aimed to evaluate new and standard endodontic antimicrobial regimens against simple and complex Candida albicans and Enterococcus faecalis mono- and dual-species biofilms. C. albicans and E. faecalis mono- and dual-species biofilms were grown upon Thermanox™ coverslips and treated for 5 min with 3% NaOCl, 3% NaOCl followed by 17% EDTA, or 9% HEDP dissolved in 3% NaOCl. The number of cells remaining immediately after treatment at 0 h and after 72 h of regrowth were assessed using real-time quantitative PCR. All three treatment arms showed a similar positive antimicrobial effect on C. albicans and E. faecalis in both mono- and dual-species biofilms following initial treatment, resulting in ≥98% reduction in colony forming equivalent (CFE). Regardless of species or biofilm type (mono- or dual- species), the antimicrobial effect of NaOCl:HEDP mixture was comparable to that of NaOCl alone, with both showing significant regrowth after 72 h, whereas sequential treatment with NaOCl and EDTA consistently prevented significant regrowth. Our data suggest that sequential irrigation with NaOCl and EDTA remains the antimicrobial strategy of choice as it significantly reduces biofilm persistence and regrowth in our experimental dual-species biofilm conditions.

Antimicrobial Activity of Phytic Acid: An Emerging Agent in Endodontics

“…EDTA is typically used as a chelating agent in root canal treatment to remove the smear layer (Calt and Serper, 2002) with a recommended contact time of 1-5 min. Despite the popularity of EDTA, the associated disadvantages of this irrigant have led to the search for alternative agents (Haapasalo (Alshanta et al, 2020). This was not attributed to the buffering effect of dentine or the complex root canal anatomy, but rather to the high tolerance of biofilm to antimicrobials (Alshanta et al, 2020).…”

“…Despite the popularity of EDTA, the associated disadvantages of this irrigant have led to the search for alternative agents ( Haapasalo et al, 2014 ). It has previously been shown that the gold standard irrigation protocol (NaOCl followed by EDTA) could not eradicate E. faecalis and C. albicans biofilms ( Alshanta et al, 2020 ). This was not attributed to the buffering effect of dentine or the complex root canal anatomy, but rather to the high tolerance of biofilm to antimicrobials ( Alshanta et al, 2020 ).…”

“…It has previously been shown that the gold standard irrigation protocol (NaOCl followed by EDTA) could not eradicate E. faecalis and C. albicans biofilms ( Alshanta et al, 2020 ). This was not attributed to the buffering effect of dentine or the complex root canal anatomy, but rather to the high tolerance of biofilm to antimicrobials ( Alshanta et al, 2020 ). It is clearly desirable therefore to identify a chelating agent with enhanced antimicrobial properties.…”

Antibacterial Effect of Sodium Hypochlorite and EDTA in Combination with High-Purity Nisin on an Endodontic-like Biofilm Model

“…This finding is in line with a previous clinical study showing that EDTA was more effective than a saline solution in reducing root canal bacteria [ 23 ]. Furthermore, sequential irrigation with NaOCl and EDTA was shown to be more efficient in reducing bacteria and preventing biofilm regrowth than NaOCl alone [ 24 ]. These findings together reinforce the benefits of using EDTA as adjunctive therapy for biofilm removal from infected root canals.…”

Filling the Void: An Optimized Polymicrobial Interkingdom Biofilm Model for Assessing Novel Antimicrobial Agents in Endodontic Infection

“…For example, Sherry and colleagues (2016) showed that combinational treatment of brushing and denture cleansing of a 11-species denture biofilm model was more effective in reducing microbial viability than singular therapies alone. To further justify our model, others have shown that endodontic treatments such as CHX, sodium hypochlorite, and EDTA were only effective against mono-species biofilms when coupled with mechanical agitation [ 47 , 48 ], and that these treatment regimens are unable to fully reduce and limit biofilm regrowth of single- and dual-species biofilms [ 49 , 50 ].…”