With human gingiva fibroblasts, the researchers investigated the adhesion of various pathogens of dental diseases. They added either an extract of red wine or grape seeds to the nutrient solution, in other cases thay added caffeic acid and coumaric acid. Small amounts of the additives were sufficient to reduce the attachment of the bacteria by 20 to 50 percent. They were able to enhance the defence effect against caries pathogens achieved by polyphenols by an addition of probiotic streptococci.