23 May 2023

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Varnish based on arginine-fluoride and its anti-cariogenic effect

Lara Figini

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Dental caries is a chronic biofilm-mediated disease and is determined by biological, behavioral, psychosocial and environmental factors. Being multifactorial in origin, dental caries has a widespread impact affecting approximately 40% of the world's population.

Strategies aimed at controlling the disease are mainly based on prevention. Fluorides (F) have long remained the main strategic intervention for caries control. The topical action of fluorine improves remineralization by facilitating the deposition of calcium (Ca2+) and phosphorus (PO43-), inhibiting demineralization and stimulating the subsequent formation of fluorapatite crystals.

However, several literature studies have highlighted a limited prolonged effect of fluoride on microbial biofilms and the development of resistance to its antimicrobial effect by cariogenic pathogens such as Streptococcus mutans. The consequence of these F limitations significantly affects patients at high caries risk who maintain cariogenic biofilms dominated by acidophilic and acidophilic bacteria.

Arginine (Arg) is a naturally occurring semi-essential amino acid, available in micromolar concentrations in saliva and plaque biofilm. Saliva and plaque metabolized by the bacterial arginolytic system arginine deaminase (ADS) go to the ammonia (NH3) pathway which helps to increase intraoral pH.

Increased ADS activity is associated with patients at low caries risk and vice versa. With increased ADS activity there is a predominance of arginolytic bacteria (Streptococcus sanguinis, Streptococcus parasanguinis and Streptococcus gordonii) in the biofilm with mild/rare acidification, thus preventing the development of cariogenic biofilms.

The amino acid L-arginine (L-Arg) has therefore been incorporated into fluoridated toothpastes, and the latter appear to provide a significantly greater protective effect against caries than toothpastes with fluoride alone.

Could this effect also apply to paints?

Materials and methods

In an experimental study, published in the March 2022 issue of the Journal of Dentistry, the authors examined the modulatory effect of arginine (Arg)-fluoride (F) varnish on a multispecies biofilm.

Experimental varnishes were prepared by incorporating L-Arg (1%, 2% and 4%) into 5% NaF sodium fluoride. The control group consisted of 5% NaF varnish alone.

The following test groups were studied:

• Group 1, 1% Arg in NaF paint (1% Arg-NaF)
• Group 2, 2% Arg in NaF paint (2% Arg-NaF)
• Group 3, 4% Arg in NaF paint (4% Arg-NaF)
• Group 4, NaF varnish (NaF) containing excipients such as ethanol, white beeswax, shellac, rosin BP, mastic, saccharin sodium, flavorings
• Group 5, no treatment.

Multispecies biofilms including Streptococcus mutans, Streptococcus sanguinis and Streptococcus gordonii were grown on hydroxyapatite (HA) discs and treated with Arg and F according to the respective concentrations of the experimental and control groups.

Biofilm thickness and live/dead bacterial counts were analyzed using images obtained by confocal microscopy, while the polysaccharide, protein and biofilm composition of extracellular DNA (eDNA) was evaluated spectrophotometrically.

The bacterial composition in the biofilms was analyzed using real-time quantitative polymerase chain reaction (qPCR). Relative gene expression (RGE) was determined for gtfB, SMU.150, nlmD, arcA and sagP.

Results

Both the 2% and 4% Arg-NaF groups reduced biofilm thickness, with the 4% Arg-NaF group showing a significantly higher proportion of dead bacteria, followed by the 1% and 2% Arg- NaF.

All Arg-NaF groups significantly reduced the carbohydrate content of the biofilm, while biofilms treated with 4% Arg-NaF showed higher concentration of eDNA and protein than the control NaF group.

The expression of gtfB, SMU.150 and nlmD was markedly reduced in biofilms treated with 4% Arg-NaF, whereas 2% Arg-NaF enhanced arcA expression. Both 2% Arg-NaF and 4% Arg-NaF significantly increased sagP expression.

Conclusions

From the data of this study, researchers concluded that incorporating L-arginine improves the modulating effect of the biofilm compared to NaF paint alone thanks to the release of Arg and f.

Clinical significance

The study results indicate that Arg-F varnish (at 2%/4% w/v. Arg) has the potential to modulate cariogenic biofilms in high-risk individuals.

For more information: "Biofilm modulatory response of arginine-fluoride varnish on multi-species biofilm."