Antimicrobial potential of Cymbopogon martinii essential oil and dental irrigant based on it against root canal biofilms

Abstract

The interest in natural products applications as antimicrobial agents is rapidly growing, mainly due to increasing microbial resistance to conventional therapeutics. Essential oils (EOs) seem to be especially attractive, since many of them possess high antimicrobial potential and none revealed resistance issue. EOs have already found applications in endodontic practice, mainly as sealers, but their antimicrobial potential has not been explored in this field yet. Taking this into account, the objective of this study was to investigate the antibacterial and antibiofilm efficacy of Cymbopogon martinii EO against bacterial strains relevant for endodontic therapy. Chemical composition of EO was determined by GC-MS/FID analysis. Antibacterial potential was screened in microdilution assay, detecting minimal inhibitory and bactericidal concentrations (MICs and MBCs) and performed on Enterococcus faecalis, Streptococcus mitis and Streptococcus sanguinis. Eradicating potential against biofilms preformed of each bacterial species as well as of all three bacteria, was determined in vitro in crystal violet (CV) assay. For screening of in situ effect against biofilm preformed in root canals of extracted teeth, the EO-based irrigant was formulated. Its antibiofilm potential was evaluated by plate counting (PC) assay, performed with single E. faecalis biofilm and multispecies biofilm composed of all three strains. Single E. faecalis biofilm was selected since it is the most relevant intracanal pathogen, while multispecies biofilm was screened to better mimic clinical conditions. Chemical analysis revealed that geraniol was the most abundant constituent (83.5%), followed by geranyl acetate (8.4%). Determined MIC and MBC values were the lowest for E. faecalis (0.12 and 0.25 mg mL-1 , respectively), and the highest for S. sanguinis (2.95 and 5.90 mg mL-1 , respectively). CV assay pointed out that EO successfully eradicated in vitro preformed biofilms of E. faecalis and S. mitis (approximately 30% reduction), but had no effect on S. sanguinis and multispecies biofilms. EO-based irrigant used for determination of in situ antibiofilm potential was pre-screened for its physicochemical characteristics: a mean particle diameter and polydispersity index was 101 ± 3 nm and 0.36 ± 0.06, respectively. PC assay showed that eradicating potential of applied irrigant was weak against both E. faecalis and multispecies intracanal biofilm (reduction of logCFU was 0.76 and 0.52, respectively). However, successive irrigation with conventional dental irrigants (sodium hypochlorite and sterile saline), followed by C. martini EO-based irrigant, notably increased the biofilm reduction (1.89 and 1.69, respectively). In conclusion, C. martini EO possesses notable antibacterial potential that could be further investigated for different dental applications.