Effect of 1-Minute Fluoride Treatment on Potential Virulence and Viability of a Cariogenic Biofilm

Abstract

Fluoride is a well-studied and widely used agent for the prevention of dental caries. Although dental caries is strongly related to cariogenic biofilms, the effect of brief fluoride treatment on the virulence properties of biofilms has not been well studied. This study evaluated the effect of a 1-min fluoride treatment on the virulence properties and viability of cariogenic biofilms, using a Streptococcus mutans biofilm model. For this study, 46-hour-old S. mutans biofilms were formed on saliva-coated hydroxyapatite discs and were treated with fluoride (0, 30, 300, 1,000, and 2,000 ppm F^-) for 1 min. Viability and changes in acidogenicity, aciduricity and extracellular polysaccharide (EPS) formation of the biofilms were analyzed using biochemical and microbiological methods (pH drop, H⁺ permeability, acid killing, and bacterial colony-forming unit assays). Laser scanning confocal fluorescence microscopy study was also performed. After the 1-min fluoride treatment, acidogenicity, aciduricity, and EPS formation of 46-hour-old S. mutans biofilms were significantly reduced when treated with concentrations ≥300 ppm F^-. The antivirulence activities of the 1-min fluoride treatment increased in a concentration-dependent pattern. However, the 1-min fluoride treatments did not affect viability, biovolume, and microcolony appearance of biofilm bacteria, even at high concentrations. These results suggest that the brief treatment with fluoride at concentrations ≥300 ppm F^- is an effective measure for controlling cariogenic biofilms.

Recovery of Acid Production in <b><i>Streptococcus mutans</i></b> Biofilms after Short-Term Fluoride Treatment

“…As reported in previous studies, fluoride was shown to reduce not only bacterial acid production in vitro but also plaque acid production in vivo [Jenkins, 1999;Vogel et al, 2002]. Furthermore, a recent study revealed that fluoride treatment clearly affects the acid production of S. mutans in biofilms at concentrations ≥ 300 ppm F - [Pandit et al, 2015]. However, information on the recovery of acid production of cariogenic bacteria after fluoride treatment is very limited, even though several studies demonstrated that fluoride inhibition of glycolysis is fully reversible [Marquis, 1995;Marquis et al, 2003].…”

“…It is well known that fluoride has inhibitory effects on the acidogenicity of cariogenic biofilms Pandit et al, 2013]. Furthermore, a recent study reported that 1-min fluoride treatment clearly affects the acidogenicity of S. mutans biofilms at concentrations ≥ 300 ppm F - [Pandit et al, 2015]. Nevertheless, another recent study revealed that dental biofilms treated with acidulated phosphate fluoride recover acid production over time [Fatemeh et al, 2014].…”

Ecological Approaches to Dental Caries Prevention: Paradigm Shift or Shibboleth?

“…Recent laboratory studies have confirmed the notion that under appropriate conditions fluoride ions can also influence critical MS virulence factors, significantly reducing acidogenicity, aciduricity, and glucan formation [Domon-Tawaraya et al, 2013;Pandit et al, 2013Pandit et al, , 2015. Metabolome analysis of plaque biofilms has demonstrated that fluoride can repress acid production in vivo too [Takahashi and Washio, 2011].…”

Characterisation of a sucrose‐independent in vitro biofilm model of supragingival plaque

“…To evaluate the acidogenicity of both sucrose‐dependent and sucrose‐independent biofilms during formation, the pH of the culture medium was measured before cultivation and then periodically over 24 hr during cultivation. To evaluate the acidogenicity of formed biofilms, a biofilm pH drop assay was performed as previously described (Pandit, Cai, Jung, & Jeon, ). In brief, 24‐hr‐old biofilms were incubated in 20 mM PBS for 1 hr to deplete endogenous catabolites, then washed twice with salt solution (50 mM KCl + 1 mM MgCl 2 , pH 7.0) and treated sequentially with 0.1% and 1.0% glucose salt solutions.…”