Objectives: To assess the antimicrobial effects of Mentha spicata and Eucalyptus camaldulensis essential oils and chlorhexidine against Streptococcus mutans and Streptococcus pyogenes, with a particular focus on in vitro and in vivo biofilm formation.
Methods: The essential oils were analysed by gas chromatography (GC) and GC-mass spectrometry. In vitro and in vivo antimicrobial and biofilm preventing activities of the oils were studied.
Results: Fifteen and 21 compounds were identified in the essential oils of M. spicata and E. camaldulensis respectively. Minimal bactericidal concentrations (MBC) of the M. spicata and E. camaldulensis oils were found to be 4 and 2 mg ml(-1), and those of chlorhexidine (2%) were 8 and 1 mg ml(-1) for both S. mutans and S. pyogenes respectively. Decimal reduction time of S. mutans by M. spicata and E. camaldulensis oils at their MBC levels was 2.8 min, while that of cholrhexidine was 12.8 min. D-value of S. pyogenes exposed to the MBC levels of M. spicata and E. camaldulensis oils and of chlorhexidine were 4.3, 3.6 and 2.8 min respectively. Antibacterial and in vivo biofilm preventive efficacies of all the concentrations of eucalyptus oil were significantly (P < 0.001) higher than that of M. spicata oil and chlorhexidine. In conclusion, essential oils are capable of affecting biofilm formation.
Conclusion: The essential oils from E. camaldulensis and M. spicata significantly retard biofilm formation that can contribute to the development of novel anticaries treatments.