This study determined the chemical components of three essential oils (cinnamon oil, clove oil and lemongrass oil) by gas chromatography and mass spectroscopy. The in vitro antifungal activity of chlorhexidine (CHX) combined with essential oils was then assessed against planktonic Candida albicans ATCC10231, Candida krusei (STCK 1) and Candida tropicalis (STCT 1) and C. albicans biofilms using broth microdilution and chequerboard assays. The results demonstrated that CHX combined with either clove oil, cinnamon oil or lemongrass oil exhibited synergistic effect against planktonic C. albicans at FICI of 0.500, 0.375 and 0.312, respectively. Additive effects were recorded for combinations tested against C. tropicalis and C. krusei. Synergistic effects were observed for clove or cinnamon oil combined with CHX (FICI 0.500 and 0.375, respectively) against sessile C. albicans in biofilm, whereas the combinations of lemongrass oil and CHX showed only additive effect (FICI 1.062). In conclusion, the combination of CHX with either clove oil or cinnamon oil may prove useful as an alternative antifungal treatment for oral Candida spp.
