Oral health is a part of general health and the two are connected in many ways as well as impact each other. Oral diseases are some of the most common chronic diseases of mankind. Diseases such as caries and periodontitis are two of the most common ones affecting the oral cavity. Bacteria associated with these two diseases are Streptococcus mutans and Aggregatibacter actinomycetemcomitans respectively. Our hypothesis is that extracts from guava leaf or matcha tea affect adhesion of A. actinomycetecomitans or S. mutans to human epithelium. The aim of this study is to investigate a DNA-based method for studying attachment of bacteria to epithelial cells. Two different concentrations of the two bacterial species, high and low, were treated with matcha or guava leaf extract and adhesion on the human epithelial cell cultures was analyzed. The results were then analyzed using qPCR-based methods to test the amount of bacterial adhesion to the epithelial cells. Furthermore, the results showed that matcha was more effective for inhibition of bacterial adhesion than guava leaf.In conclusion, our results show that bacterial adhesion of A. actinomycetecomitans and S. mutans to human epithelial cells can be quantified by DNA-based methods, and the adhesion altered by plant extracts.