Mouth-rinsing solutions and Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis biofilms

Objectives: The study was aimed to compare the efficacy of different mouthrinse-solutions with chlorhexidine against periodontopathogens within a single-species biofilm. Methods: Biofilms of six strains (3 A. actinomycetemcomitans (Aa) and 3 P. gingivalis (Pg)) were established over five days. Then the biofilms were exposed to the different rinsing solutions (Meridol, NovaTop, Delmopinol, 0.06, 0.1 and 0.2% chlorhexidine digluconate (CHX) and 0.9% NaCl as control) for 1 min. Thereafter the solution was removed and nutrient broth was added again. 24 and 48 h later, the colony forming units (cfu) within the biofilms were determined. Statistical analysis was made by using ANOVA with post-hoc Bonferroni test for each strain. Results: All rinsing solutions significantly reduced the cfu counts by at least 3.5 log-stages, a complete killing was never found. Differences between 24 and 48 h after application of the solutions were extremely low and did not reach significance. CHX solutions showed a concentration-dependent effect. 0.1 and 0.2% CHX solutions were most efficient and showed superiority against Meridol and NovaTop for all tested strains and against Delmopinol and 0.06% CHX for each 2 Aa and 2 Pg strains. Conclusion: Although diverse mouth-rinsing solutions act antibacterial, CHX still represents the gold-standard in activity against bacteria within biofilm. Nevertheless a complete killing of bacteria within biofilm by disinfectants is impossible.