Antimicrobial efficacy of cinnamon essential oil on the oral microbiome: A systematic review of in vitro studies

Cinnamon essential oil (CEO) is a promising natural antimicrobial agent for treating oral diseases. This systematic review evaluated the antimicrobial efficacy of CEO against major oral microbiome bacteria. A comprehensive search was conducted in PubMed, Scopus, Embase, ScienceDirect, and DOAJ, selecting in vitro studies with no publication date restrictions that examined the effect of CEO on bacterial strains associated with dental caries and periodontal disease. The quality assessment tool for in vitro studies (QUIN) was used for risk-of-bias assessment, and the grading of recommendations assessment, development and evaluation (GRADE) was used to assess the certainty of evidence. After screening, 13 studies were included. In the final synthesis of results, CEO exhibited significant bactericidal activity, especially against Streptococcus mutans and Candida albicans, and reduced cell viability at low minimum inhibitory concentrations. Most in vitro studies demonstrated a dose-dependent response, with higher concentrations of the oil producing more pronounced antimicrobial effects. Several studies reported morphological alterations in microbial cells exposed to the oil, indicating membrane disruption as a possible mechanism of action. In addition, the essential oil was effective against biofilm-forming strains, suggesting its potential use in managing dental plaque and oral infections. Our findings suggest that CEO could represent a complementary option for the prevention and treatment of oral diseases; however, more clinical studies are needed to validate its efficacy and safety in patients.