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