The combined antimicrobial effect of arginine and fluoride toothpaste

The aim of the study was to investigate the antibacterial effect of arginine (Arg) in NaF toothpaste. 24-h mono-/3-species biofilm cultures of S. mutans, S. sanguis and S. gordonii inoculated sHA discs were subjected to treatment with toothpaste supernatants prepared as - [1]:2% Arg -NaF (0.147% F), [2]:4% Arg-NaF (0.144% F), [3]:8% Arg - NaF (0.138% F), [4]:NaF (0.15%) and [5]:deionized water. After 24-h incubation, the mono-species biofilms were subjected to viability assay using WST-8, SEM and confocal imaging (CLSM). The 3-species biofilm were quantified for bacterial composition by PCR analysis, SEM, CLSM, and RNA isolation with reverse-transcription PCR analysis. Increasing arginine concentrations in NaF toothpaste had no effect on microbial viability. The mono-/3-species biofilm imaging depicted that the 2% Arg-NaF and 4% Arg-NaF had a biofilm disrupting effect. The 3-species biofilm bacterial composition indicated that the 2% Arg-NaF group maintained an ecological homeostasis by inhibiting S. mutans growth and enriching the growth of S. sanguis and S. gordonii. The 2% Arg-NaF group significantly downregulated the expression of virulent gtfB gene and upregulated the expression of sagP with relative dominance of arcA. Incorporation of 2% arginine in NaF toothpaste might enrich the alkali-producing bacteria and provide enhanced counter mechanisms against cariogenic pathogen when compared to NaF toothpaste.