Effect of Mouth Rinsing and Antiseptic Solutions on Periodontitis Bacteria in an In Vitro Oral Human Biofilm Model

<b>Background/Objectives</b>: The formation of oral biofilms in periodontal pockets and around dental implants with induction of periodontitis or peri-implantitis is an increasing problem in dental health. The intelligent design of a biofilm makes the bacteria embedded in the biofilm matrix highly tolerant to antiseptic therapy, often resulting in tooth or implant loss. The question therefore arises as to which mouthwashes have eradication potential against oral biofilm. <b>Methods</b>: A human oral biofilm model was developed based on donated blood plasma combined with buffy coats, inoculated with oral pathogenic bacterial species found in periodontal disease (<i>Actinomyces naeslundii</i>, <i>Fusobacterium nucleatum</i>, <i>Streptococcus mitis</i>, and <i>Porphyromonas gingivalis</i>). Over a span of 7 days, we tested different mouth rinsing and antiseptic solutions (Chlorhexidine, Listerine^®, NaOCl, Octenisept^®, and Octenident^®) covering the matured biofilm with 24 h renewal. Phosphate-buffered saline (PBS) was used as a control. Bacterial growth patterns were detected via quantitative polymerase chain reaction (qPCR) after 2, 4, and 7 days of treatment. <b>Results</b>: While all groups showed initial bacterial reduction, the control group demonstrated strong regrowth from day 2 to 4. Listerine showed a near-significant trend toward bacterial suppression. Additionally, strain-specific efficacy was observed, with Octenisept^® being most effective against <i>Streptococcus mitis</i>, Octenident^® and NaOCl showing superior suppression of <i>Actinomyces naeslundii</i>, and Listerine^® outperforming other solutions in reducing <i>Fusobacterium nucleatum</i>. Donor-specific, individual variability further influenced treatment outcomes, with distinct trends in bacterial suppression and regrowth observed across donors. <b>Conclusions</b>: These findings underscore the complexity of biofilm-associated infections and highlight the importance of targeted therapeutic approaches for managing bacterial biofilms. In this experiment, the donor-specific outcomes of the antimicrobial effects of the solutions may indicate that genetic predisposition/tolerance to oral infections appears to play a critical role in the control of oral biofilms.