The Combined Antimicrobial Effect of Arginine and Fluoride

Objectives: Arginine in NaF toothpaste might regulate ecological homeostasis for anti-caries benefit compared to NaF (alone) especially in high-risk patients. Hence, the aim of the present study was to examine the antimicrobial effect of arginine (Arg) in NaF toothpaste on mixed-species biofilm.

Methods: Mixed-species biofilm cultures of Streptococcus mutans, Streptococcus sanguis and Streptococcus gordinii were inoculated on saliva coated hydroxyapatite discs (sHA). The anti-caries effect of toothpaste slurries prepared as: [1]: 2% Arg – NaF, [2]: 4% Arg – NaF, [3]: 8% Arg – NaF, [4]: NaF and [5]: deionized water was evaluated on 24-h sHA cultured three-species biofilm. After 24-h post-treatment inoculation, the discs were quantified for bacterial composition by species specific real-time quantitative polymerase chain reaction (qPCR). Biofilm imaging was done using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). All experiments were replicated twice at disparate time points.
Results: qPCR analysis (CFU/ml) revealed that 2% Arg – NaF demonstrated maximal inhibition of Streptococcus mutans with subsequent increase in Streptococcus sanguis and Streptococcus gordinii. DI water preceded by NaF displayed least effect on Streptococcus mutans limiting growth of non-mutans streptococci (Streptococcus sanguis and Streptococcus gordinii). SEM analysis exhibited that 2% Arg – NaF and 4% Arg – NaF had a disruptive effect on the biofilm. CLSM derived live/dead ratio presented significant difference between 8% Arg – NaF and NaF with no difference between arginine-based slurries.
Conclusions: Incorporation of 2% Arginine in NaF toothpaste might help maintaining better ecological homeostasis by up regulating the non-mutans streptococci with simultaneous suppression of Streptococcus mutans when compared to other treatments evaluated in the study. Thus, Arginine supplementation to NaF can help enrich the arginine deiminase system positive bacteria to effectuate neutral pH and provide counter mechanisms against cariogenic pathogens. Hence, 2% Arg-NaF toothpaste might provide an enhanced antimicrobial effect against caries-generating bacteria (using pre-biotic approach) compared to NaF (alone) especially in high-risk individuals.