Influence of Medicinal Plant Extracts on the Growth of Oral Pathogens Streptococcus Mutans and Lactobacillus Acidophilus: An In-Vitro Study

AIM: This study investigated the antibacterial efficacy of five plant extracts, as well as the combinations of the two most effective plant, extracts either with or without commercial varnish (MI varnish) on the in vitro growth of Streptococcus mutans and Lactobacillus acidophilus in comparison to MI varnish using agar disk diffusion and broth dilution methods. METHODS: Methanolic extractions of five plants (Cinnamon, Turmeric, Ginger, Clove and Black seed,) were tested against the growth of the two oral pathogens. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for the two most effective extracts, and their combinations with different ratios were evaluated against the growth of the two oral pathogens, followed by incorporating the two effective plants or each into commercial MI varnish to be assessed against the oral pathogens in comparison to MI varnish. RESULTS: Only Cinnamon and Clove produced inhibition zones against Streptococcus mutans and Lactobacillus acidophilus growth. MIC for the two plants showed equal antimicrobial activity against Streptococcus mutans, while Cinnamon had a higher sensitivity to Lactobacillus acidophilus than Clove. A mixture of Cinnamon and Clove in a ratio 1:2 exhibited the highest antibacterial activity. Integration the mixture of both plants into MI varnish in a ratio of 1:1:1 presented the highest antibacterial activity. Meanwhile, the lowest one was recorded for the MI varnish alone. CONCLUSION: Methanolic extract of Cinnamon and Clove has considerable antimicrobial activity against Streptococcus mutans and Lactobacillus acidophilus and a new tool for minimally invasive and adhesive dentistry avenues.