Control of microorganisms in vitro by endodontic irrigants

Abstract

The aim of this study was to determine the minimum inhibitory concentration (MIC) and antimicrobial effectiveness by the direct exposure test of 4 endodontic irrigants [1% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 1% calcium hydroxide (Ca(OH) 2; prepared with 1 g of Ca(OH) 2 and 100 mL of sterile distilled water), a solution of Ca(OH) 2 + detergent (HCT20)] for S. aureus, E. faecalis, P. aeruginosa, B. subtilis, C. albicans and a mixed culture. Microbial growth was analyzed by two methods: turbidity of the culture medium that was confirmed by Gram stain and subculture in a specific nutrient broth. In the dilution test, NaOCl solution showed MIC equal to 0.1% for S. aureus, E. faecalis, P. aeruginosa and C. albicans and equal to 1% for B. subtilis and the mixed culture. CHX (2%) presented MIC equal to 0.000002% for S. aureus, 0.02% for E. faecalis, B. subtilis, C. albicans and the mixed culture and 0.002% for P. aeruginosa. Ca(OH) 2 solution (1%) showed MIC greater than 1% for all the microorganisms except P. aeruginosa for which it was equal to 1%. Calcium hydroxide solution + detergent showed MIC equal to 4.5 mL for S. aureus, P. aeruginosa, B. subtilis, C. albicans and the mixed culture and greater than 4.5 mL for E. faecalis. In the direct exposure test, NaOCl had better antimicrobial effectiveness for all microorganisms at all times. CHX (2%) was effective for S. aureus, E. faecalis and C. albicans at all times, and ineffective for P. aeruginosa, B. subtilis and the mixed culture. The other solutions showed the worst results.

Characterization of Successful Root Canal Treatment

“…This fact reinforces the concept of eliminating empty spaces that can harbor microorganisms (8,9,23,24). The RCT excellency is associated with the disinfection process, which involves removing microorganisms from the root canal system by emptying, cleaning and enlarging/shaping, combined with the use of antibacterial therapies (8,9,16,23,25,26). Based on the need to control the microbiota of infected root canals, some aspects are necessary in a therapeutic protocol.…”

“…The antimicrobial effect of sodium hypochlorite by direct contact with E. faecalis occurs after 2 min (25). The positive culture of microorganisms following the application of the irrigating solutions (ozonated water, gaseous ozone, 2.5% sodium hypochlorite, 2% chlorhexidine) for 20 min confirmed their inability to sterilize an infected human root canal (24).…”

“…The selection of an ideal irrigant depends on its action against the root canal microbiota and the biological effect on periapical tissue (24,25,40). Several irrigating solutions have been considered in order to decrease endodontic infection and contribute to canal disinfection, including: halogenated compounds (sodium hypochlorite), chlorhexidine, detergents (anionic, cationic), chelating agents (EDTA, citric acid), MTAD, ozonated water, apple vinegar.…”

“…Several irrigating solutions have been considered in order to decrease endodontic infection and contribute to canal disinfection, including: halogenated compounds (sodium hypochlorite), chlorhexidine, detergents (anionic, cationic), chelating agents (EDTA, citric acid), MTAD, ozonated water, apple vinegar. However, up to now, sodium hypochlorite and chlorhexidine are the most often indicated antimicrobial agents for treatment protocols against endodontic and periodontal infections (24,25,40).…”

Shelf-life of a 2.5% sodium hypochlorite solution as determined by arrhenius equation

“…Vianna et al (3) and Estrela et al (4,5) showed that sodium hypochlorite is more bactericidal than chlorhexidine gel. In terms of tissue dissolution, efficiency is proportional to hypochlorite concentration in the solution (6,7).…”