Antimicrobial potential of irrigants based on essential oils of Cymbopogon martinii and Thymus zygis towards in vitro multispecies biofilm cultured in ex vivo root canals

Objective: The objective was to determine the antibiofilm efficacy of Cymbopogon martinii and Thymus zygis essential oils and to estimate the disruption potential of oil-based endodontic irrigants on the multispecies biofilm formed in the root canals of extracted teeth.

Design: The essential oils were characterized (GC-MS), while their antibacterial and cytotoxic properties were detected by microdilution and MTT assays. Particles sizes and polydispersity indices were determined for the irrigants. The isolates from root canals of pediatric patients were identified (MALDI-TOF). The multispecies biofilms were formed from Streptococcus mitis, Streptococcus sanguinis and Enterococcus faecalis. Antibiofilm properties of the essential oils and irrigants were determined by crystal violet and plate counting assay. Statistical analysis was performed by one-way ANOVA.

Results: The screening of biofilm biomass revealed a disruption potential of C. martinii essential oil. The plate counting assay showed the efficacy of both oils in diminishing cell viability: high in biofilms (reduction of log₁₀CFU was 2.75-2.87) and moderate in the planktons formed above. The essential oil-based irrigants showed the same antibiofilm activity as in the control (1.5 % sodium hypochlorite) for C. martini and almost 2-fold higher for T. zygis. Successive irrigations with 1.5 % sodium hypochlorite, saline and an oil-based irrigant was more efficient for C. martini than for the control (reductions of log₁₀CFU was 1.69 and 1.14, respectively).

Conclusions: Notable activities achieved by essential oils and oil-based irrigants, particularly regarding C. martini, against the biofilm consisting of S. mitis, S. sanguinis, and E. faecalis, are expected to encourage further research in endodontics.