Background: Oral infections and dental caries are significant health concerns, especially in developing countries. Streptococcus mutans and Candida albicans play key roles in dental caries and oral fungal infections, while chlorhexidine may have side effects. Plant-derived compounds such as Mentha longifolia essential oil are therefore being explored as alternative or adjunctive therapies. This study compared the antimicrobial effects of Mentha longifolia essential oil and chlorhexidine.
Methods: In 2025, an in vitro study was conducted at the Bacteriology Laboratory of Ahvaz University of Medical Sciences on S. mutans PTCC1683 and C. albicans PTCC10231 obtained from Iranian bacterial and fungal collections. Minimum inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC), and microbial killing times were determined for both agents.
Findings: For S. mutans, MIC values were 0.035 µg/mL for chlorhexidine and 108.33 µg/mL for Mentha longifolia oil, with MBCs of 0.03 and 223.33 µg/mL, respectively. Both agents completely eradicated bacteria within 5 hours. For C. albicans, MICs were 0.56 µg/mL (chlorhexidine) and 7290.66 µg/mL (Mentha longifolia oil), with MFCs of 2.27 and 14583.33 µg/mL, respectively; Mentha longifolia oil eliminated the fungus within 1 hour, while chlorhexidine required 24 hours.
Conclusion: Chlorhexidine exhibited stronger inhibitory and bactericidal/fungicidal effects at lower concentrations. Nonetheless, Mentha longifolia essential oil demonstrated significant antimicrobial activity and may serve as a complementary option in future studies.