Figure 1. Flowchart of the study design from screening to follow-up.

After a baseline visit, eligible volunteers were scheduled for intensive professional tooth cleaning and oral hygiene instructions to remove all biofilm deposits before starting the experimental gingivitis phase. After 21-days of cessation from any oral hygiene procedures in the upper right maxilla massive bacterial biofilms has been formed on the selected tooth hard substances, which are visible to the naked eye as yellowish plaques. Plaque covering of the tooth was routinely documented after erythrosine staining. The professional removal of all bacterial deposits and the restart of oral homecare terminated the experimental gingivitis phase. At baseline, day 21 (gingivitis) and 21 days after completion of the experimental gingivitis phase (follow-up) blood samples were obtained for serum parameters and monocyte activation assays.