Comparative Evaluation of Influence of Different Concentrations of Chlorhexidine Mouthrinses Against Porphyromonas Gingivalis and Fusobacterium Nucleatum: An in-Vitro Study

Background: Periodontal pathogens such as Porphyromonas gingivalis and Fusobacterium nucleatum are most dominant in the aetiology of chronic periodontitis and peri-implantitis. This in-vitro study determined the time-dependent bactericidal efficacy of two most used chlorhexidine products (0.2% and 0.12%) against these pathogens under anaerobic conditions. Methods: Standardized suspensions of F. nucleatum and P. gingivalis were treated with 0.2% and 0.12% chlorhexidine mouthrinses and 0.9% saline, used as control. All experimental conditions were tested in triplicates, and microbial inocula were grown on blood agar and incubated at 37°C in a CO₂ anaerobic chamber. Microbial quantification of colony-forming units (CFUs) was performed at 0, 1, 2, 5, 10, and 15 minutes. One-way ANOVA with post-hoc Tukey tests were utilized for data analysis, and significance was established at p < 0.05. Results: The 0.2% chlorhexidine mouthrinse showed an immediate and complete reduction in F. nucleatum at 1 minute (CFU reduction from 131.3 ± 3.51 to 0.0 ± 0.0; p < 0.001), while the 0.12% solution showed complete kill of bacteria by 5 minutes, with a more gradual early reduction (113.3 ± 9.07 to 88.6 ± 3.05 at 2 minutes; p < 0.001). Saline had no significant reductions at all time points. With P. gingivalis, both concentrations of chlorhexidine showed total bactericidal activity at 5 minutes. Interestingly, the 0.12% preparation showed more reduction between 1 and 2 minutes (214.33 ± 10.96 to 62.66 ± 5.03), while the 0.2% rinse showed more of a gradual reduction (284.33 ± 7.63 to 199.3 ± 6.02 at 2 minutes). Conclusion: Both concentrations of chlorhexidine exhibited excellent antimicrobial activity against F. nucleatum and P. gingivalis with complete killing in 5 minutes. The 0.2% solution showed faster bactericidal activity, especially against F. nucleatum, which worked better with short contact times.