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.
Table 1.
Species-specific primers used to identify ten different bacterial species in plaque samples of experimental gingivitis at day 21 of the study.
Table 2.
Baseline characteristics of the patients.
Figure 2.
Characterization of oral clinical parameters at baseline and after 21 days of experimental gingivitis.
The box-plots illustrate the plaque accumulation on tooth hard-substances during the 21-days non-brushing period followed by the progression of three selected clinical inflammatory parameters documenting the inflammatory status of the gingival tissues. The time interval and clinical observations are characteristic for an inflammatory lesion denoted as gingivitis.
Figure 3.
Species-specific detection of bacteria in 21-day old dental biofilms.
The box-plots represent the PCR-based detection frequency of ten representative bacterial species within the study population of 37 subjects. The colors of the bars comply with the color codes of the bacterial complexes introduced by Socransky et al. [20].
Figure 4.
Characterization of serum parameters of inflammation at baseline, experimental gingivitis and follow-up.
(A) Serum of participants was analyzed for hsCRP by immunonephelometrie. Plasma of participants was analyzed for IL-6 (B) and MCP-1 (C) by ELISA. Serums of participants were analyzed for leucocyte (D) and monocyte (E) cell counts by flow cytometry. P-values were calculated using two-sided Wilcoxon signed-rank tests for paired samples.
Figure 5.
Monocyte adhesion assays and foam cell formation at baseline, gingivitis and follow-up.
Blood monocytes were isolated from the blood of the volunteers at baseline (day 0), gingivitis (day 21) and follow-up (day 42) and subjected to ex vivo activation assays. (A) Number of adherent monocytes on cultured endothelial cells (HUVECs). Arrowheads in the enlarged picture detail indicate adherent monocytes. (B) Percentage foam cell formation after stimulation with oxLDL (10 µg/ml). Arrowheads indicate oil red O-positive foam cells. Representative pictures are shown. P-values were calculated using two-sided Wilcoxon signed-rank tests for paired samples.