Antibacterial Efficacy of Alternative and Conventional
Endodontic Irrigants on S.mutans and E.faecalis
INTRODUCTION
Microorganisms are the main factor in the etiology of periapical
pathology (Kakehashi et al., 1965). Therefore, endodontic treatment aims
to chemomechanically minimize bacteria in the root canal system and
optimally seal the root canal space to prevent recontamination (Bystrom
& Sundqvist, 1981). The persistence of microorganisms after endodontic
treatment causes failure, therefore irrigation solutions with
bactericidal properties are used during treatment (Pace et al., 2020;
Siqueira, 2001). There are many root canal irrigation solutions on the
market with different contents and properties.
Sodium hypochlorite (NaOCl) and chlorhexidine (CHX) are widely used in
endodontic treatment and there are many studies in the literature. NaOCl
has an effective organic tissue solvent and disinfection effect at high
concentrations (Ayhan et al., 1999). CHX is an endodontic irrigation
solution with broad spectrum antimicrobial activity, substantivity, and
strong antiseptic properties. Although there are in-vitro cytotoxicity
studies indicating that CHX has a higher cytotoxic effect than NaOCl
(Trevino et al., 2011), there are also studies stating the opposite
(Mollashahi et al., 2016). Due to the toxic effects of NaOCl and CHX on
vital tissues, alternative irrigation solutions are being investigated.
Hypochlorous Acid (HOCl) has been suggested as an alternative irrigation
solution to NaOCl because it provides effective cleaning of the root
canal walls (Solovyeva & Dummer, 2000). There are also studies
recommended for the disinfection of endoscopes, water systems of dental
units, and dental impression materials (Rossi-Fedele et al., 2010). In a
study, HOCl was compared with NaOCl and it was reported that they showed
similar antibacterial activity on E.faecalis, however, HOCl
showed much lower toxicity than NaOCl (Hsieh et al., 2020).
Polyhexamethylene biguanide or polyhexanide (PHMB) is an alternative to
CHX (Santos et al., 2021). It has a wide spectrum of antimicrobial
activity, the ability to adhere to the organic matrix, good cell and
tissue tolerance, low-grade contact sensitivity risk, and wound healing
stimulating effect (Arican et al., 2020; Eberlein & Assadian, 2010;
Kramer et al., 2018).
In the literature, there is no study examining and comparing the
antibacterial effects of conventional solutions and relatively new
alternative root canal irrigation solutions on cariogenic bacteria. This
study aimed to evaluate the in-vitro antibacterial activities of
alternative and conventional endodontic irrigation solutions againstEnterococcus faecalis and Streptococcus mutans when used
alone or in combination.
MATERIAL and METHOD
The following commercially available irrigation solutions were
evaluated: 5.25% sodium hypochlorite (NaOCl; Endosolve HP, Imicryl,
Turkiye); 2% chlorhexidine (CHX; Ceraxidin-C, Imicryl, Turkiye); 0.02%
(200 ppm) hypochlorous acid (HOCl; Crystalin, Natural Health
Products-NHP, Turkiye); 0.1% Polyhexanide (PHMB; Actolind® w Solution,
ACTO Pharma, Germany). Sterile saline was used as a negative control.
Standard strains of Streptococcus mutans (ATCC 25175) andEnterococcus faecalis (ATCC 29212) were used in the study, and
the strains were incubated in Columbia Agar with 5% sheep blood agar
(Becton Dickinson, GmbH) at 37oC for 24-48 hours.
Antiseptics were impregnated on disk-shaped filter papers. Then, these
discs were placed first separately and then in pairs to investigate the
synergistic effects of antiseptics when used alone or together, and the
zone diameters were measured by the Kirby Bauer disc diffusion method.
RESULTS
In S.mutans, 20mm inhibition zone diameter was measured for both
CHX and HOCl when used alone, and the highest antimicrobial activity was
observed. Approximately the same efficacy was observed in NaOCl (6mm)
and PHMB (5mm). The highest efficacy was observed in CHX+HOCl (20mm) in
combined use. Inhibition diameters of irrigation solutions onS.mutans as a result of the single- and double-disc synergy
method are shown in Table 1.
Tablo 1. Inhibition diameters of irrigation solutions on S.mutans