Inhibitory Efficacy of Thymus vulgaris and Origanum onites Essential Oils on Enterococcus faecalis Biofilm

Objective: The crucial aim of irrigation solutions used in root canal treatments is the elimination of biofilm which is considered an important virulence factor of Enterococcusfaecalis. Essential oils have been investigated to understand their efficacy for biofilm elimination in recent years. This study aimed to evaluate the antimicrobial and antibiofilm effects of Thymus vulgaris essential oils (TEO) and Origanum onites essential oils (OEO) on E. faecalis. Methods: The antimicrobial effectiveness of TEO and OEO against E. faecalis (ATCC 29212) was investigated by broth microdilution method, and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. The effect of TEO and OEO on preventing biofilm formation was evaluated by measuring biofilm biomass using crystal-violet method, and its effect on biofilm viability was evaluated by determining the number of living cells in the biofilm as colony-forming units. Biofilm viability was analyzed with one-sample t-test with statistical significance accepted as p<0.05. Results: The MIC values ​​of TEO and OEO were determined as 0.078 µL/mL, and MBC values ​​were determined as 0.156 µL/mL for OEO and 0.078 µL/mL for TEO. The percentage inhibition of biofilm formation at MIC value for OEO and TEO was determined as 53.9% and 55.6%, respectively. Both essential oils caused a significant reduction in the number of viable cells within the biofilm. Conclusion: It is concluded that TEO and OEO show high antimicrobial and antibiofilm activity against E. faecalis biofilm. Therefore, these essential oils can be considered an alternative irrigation solution for eliminating resistant root canal infections.