In vitro effect of mouthwash containing chlorhexidine and chlorine dioxide against halitosis pathogens

Objective This study evaluated the antibacterial efficacy of chlorhexidine-chlorine dioxide (CHX-CDO) mouthwash formulations against major halitosis-related pathogens: Porphyromonas gingivalis (Pg), Aggregatibacter actinomycetemcomitans (Aa), Fusobacterium nucleatum (Fn), Prevotella intermedia (Pi), and Eikenella corrodens (Ec). Materials and methods Five bacterial strains were cultured anaerobically. Experimental mouthwashes with varying concentrations of CHX (0.01–0.2%) and CDO (0.05–0.1%), labeled solution A–J, were tested. Agar diffusion assays measured inhibition zones. MICs were determined by broth microdilution with 24 h anaerobic incubation and OD600 measurement. The time-kill test quantified CFUs from serial dilutions at time points (0, 1, 3, 6, 12, and 24 h). Results All CHX-CDO mouthwash combinations inhibited bacterial growth, with A (0.05% CHX + 0.05% CDO), C (0.2% CHX + 0.05% CDO), F (0.2% CHX + 0.1% CDO), and J (CHX 0.02/CDO 0.1) showing the largest inhibition zones and G (CHX 0.01/CDO 0.05) and H (CHX 0.02/CDO 0.05) exhibiting the most favorable MIC values. Time-kill assays confirmed sustained bactericidal effects for low concentration-CHX/0.05% CDO formulations. Significant differences in antibacterial activity were observed among the formulations (p < 0.05). Conclusion Low-dose CHX combined with 0.05% CDO mouthwash maintains antibacterial efficacy against halitosis-associated pathogens, suggesting a promising CHX dose reduction while preserving effectiveness.