At baseline those identified P.g. positive participants received a supragingival debridement (professional tooth cleaning) and were randomly assigned to the test- or control-group. Afterwards the study participants are instructed to rinse 3 times per day with 10 ml of either Rumex acetosa L. extract mouth rinse or the placebo mouth rinse for 7 days in addition to their oral hygiene procedures. Plaque samples were taken at different visits (screening, baseline, 2, 4, 7 and 14 days after baseline) and P.g. was identified and quantified by real-time polymerase chain reaction (qrt-PCR). Also the relative quantity of eight other oral pathogenic microorganisms (Aggregatibacter actinomycetemcomitans, Treponema denticola, Tannerella forsythia, Prevotella nigrescens, Prevotella intermedia, Eikenella corrodens, Streptococcus mutans and Candida albicans) and four commensal bacteria (Streptococcus sanguinis, Streptococcus mitis, Veillonella parvula and Actinomyces viscosus) was determined over the whole study period by qrt-PCR. Additionally clinical parameters, i.e. the Approximal Plaque Index (API) and the modified Sulcular Bleeding Index (SBI) were recorded at baseline, 7 and 14 days. For identifying any dysplastic changes and mutations as a potential reaction to the tested mouthwash solutions brushing biopsies of the oral mucosa were taken at baseline and day 7 and were histologically examined.