Researchers have found in a new study that organic refined, organic virgin, and extra virgin coconut oils, along with uplifting frankincense essential oil, demonstrated effective in-vitro antimicrobial activity against Streptococcus mutans. Among all tested agents, uplifting frankincense essential oil showed the greatest reduction in S. mutans biofilm formation.Dental caries is a disease influenced by multiple factors. Elements such as diet, the shape and structure of teeth, the oral environment, and the presence of certain microorganisms all contribute to the development of dental caries. Among such microorganisms, Streptococcus mutans (S. mutans) is a facultative anaerobic, gram-positive bacterium known for its strong association with dental caries due to its high virulence. Its ability to adhere to tooth enamel, produce acidic byproducts, store glycogen, and generate extracellular polysaccharides contributes significantly to its role in tooth decay. Several methods have been investigated to prevent dental caries by targeting the formation of cariogenic biofilms through the application of antimicrobial agents. This study aimed to investigate the antibiofilm effect of coconut and frankincense oils. Different types of coconut (organic refined, cocos nucifera, organic virgin, and organic extra virgin) and frankincense (frankincense pure essential oil in fractionated coconut oil and uplifting frankincense pure essential) oils were investigated. Serial dilutions (1:3, 1:6, 1:12, 1:24, 1:48, 1:96, and 1:192) were created from each oil and incubated with an overnight culture of S. mutans. The total growth and biofilms absorbance were measured at 595 and 490 nm, respectively. One-way ANOVA and Tukey tests were used for data analysis.Results: The greatest biofilm inhibition was observed in the uplifting frankincense pure essential oil at 1:3 dilution (0.67±0.12), which was significantly lower (p<0.01) than the control (1.51 ± 0.07). In addition, organic refined (0.96±0.13), organic virgin (1.21±0.28), and organic extra virgin (1.07±0.17) were associated with less biofilms compared to the control, but without a statistical significance. Frankincense pure essential oil in fractionated coconut oil and cocos nucifera coconut oil did not show biofilm inhibition.Organic refined, organic virgin, and extra virgin coconut oils, and uplifting frankincense essential oil, effectively reduced S. mutans levels in vitro, with the highest amount of biofilm reduction associated with uplifting frankincense essential oil.Reference:Alghamdi N, Alshamrani L, Alboryah S et al. The Effect of Coconut and Frankincense Oils on the Biofilm Growth of Streptococcus mutans [version 1; peer review: 2 approved, 1 approved with reservations]. F1000Research 2025, 14:846 (https://doi.org/10.12688/f1000research.168621.1)Keywords:Essential oils, biofilm, caries, gingivitis, mouthrinse, Alghamdi N, Alshamrani L, Alboryah S