Evaluation of Streptococcus mutans adhesion to fluoride varnishes and subsequent change in biofilm accumulation and acidogenicity

Objectives

The aim of this study was to evaluate Streptococcus mutans adhesion to fluoride varnishes and subsequent change in biofilm accumulation and acidogenicity.

Methods

After producing fluoride varnish-coated hydroxyapatite discs using Fluor Protector (FP), Bifluorid 12 (BIF), Cavity Shield (CASH), or Flor-Opal Varnish White (FO), S. mutans biofilms were formed on the discs. To assess S. mutans adhesion to the discs, 4-h-old biofilms were analysed. To investigate the change in biofilm accumulation during subsequent biofilm formation, the biomass, colony forming units (CFU), and water-insoluble extracellular polysaccharides (EP) of 46-, 70-, and 94-h-old biofilms were analysed. To investigate the change in acidogenicity, pH values of the culture medium were determined during the experimental period. The amount of fluoride in the culture medium was also determined during the experimental period.

Results

BIF, CASH, and FO affected S. mutans adhesion (67–98% reduction) and subsequent biofilm accumulation in 46-, 70-, and 94-h-old biofilms. However, the reducing effect of the fluoride varnishes on the biomass, CFU count, water-insoluble EP amount, and acid production rate of the biofilms decreased as the biofilm age increased. These results may be related to the fluoride-release pattern of the fluoride varnishes. Of the fluoride varnishes tested, FO showed the highest reducing effect against the bacterial adhesion and subsequent biofilm accumulation.

Conclusions

Our findings suggest that if the results of these experiments are extrapolable to the in vivo situation, then reduced clinical benefit of using fluoride varnishes may occur with time.

Clinical significance

Fluoride varnish application can affect cariogenic biofilm formation but the anti-biofilm activity may be reduced with time.     

Effect of sodium fluoride on the virulence factors and composition of Streptococcus mutans biofilms

Objective

This study aimed to evaluate the influence of NaF (2, 10, 50 and 125 ppm F⁻) on the virulence factors and composition of Streptococcus mutans biofilms.

Methods

S. mutans UA159 biofilms were formed on saliva-coated hydroxyapatite discs. To assess the influence of NaF on the virulence factors of S. mutans biofilm cells, glycolytic pH drop, proton-permeability and F-ATPase activity assay were performed using 74 h old S. mutans biofilms. Glucosyltransferase (GTF) activity assay in suspension was also performed. To examine the influence of NaF on S. mutans biofilm composition, the biofilms were treated twice daily (5 min exposure/treatment) a total of five times during biofilm formation. After a total of 5 treatments, the biomass, colony forming unit (CFU) and polysaccharide composition of the treated 74 h old S. mutans biofilms were analysed by microbiological and biochemical methods, and scanning electron microscopy.

Results

NaF showed inhibitory effects on the acid production and acid tolerance of S. mutans biofilm cells at 10, 50 and 125 ppm F⁻, compared to the vehicle control (P < 0.05) and the treatments at these concentrations also affected the biomass, water-insoluble extracellular polysaccharides and intracellular iodophilic polysaccharides of the biofilms, compared to the vehicle control (P < 0.05).

Conclusions

These results indicate that NaF (10, 50 and 125 ppm F⁻) has inhibitory effects on the virulence factors and composition of S. mutans biofilms, suggesting the potential use of these concentrations as an effective measure for controlling dental biofilms.     

Effect of arginine on the growth and biofilm formation of oral bacteria

BackgroundAlkali production via arginine deiminase system (ADS) of oral bacteria plays a significant role in oral ecology, pH homeostasis and inhibition of dental caries. ADS activity in dental plaque varies greatly between individuals, which may profoundly affect their susceptibility to caries.ObjectiveTo investigate the effect of arginine on the growth and biofilm formation of oral bacteria.Methods and resultsPolymicrobial dental biofilms derived from saliva were formed in a high-throughput active attachment biofilm model and l-arginine (Arg) was shown to reduce the colony forming units (CFU) counts of such biofilms grown for various periods or biofilms derived from saliva of subjects with different caries status. Arg hardly disturbed bacterial growth of Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis and Streptococcus gordonii in BHI medium, but only inhibited biofilm formation of S. mutans. Scanning electron microscope (SEM) showed S. mutans biofilms harboured fewer cells grown with Arg than that without Arg, even in the initial 2 h and 8 h phase. Confocal laser scanning microscope (CLSM) images of poly-microbial dental and S. mutans biofilms revealed the biofilms grown with Arg had lower exopolysaccharide (EPS)/bacteria ratios than those without Arg (P = 0.004, 0.002, respectively). Arg could significantly reduce the production of water-insoluble EPS in S. mutans biofilms (P < 0.001); however, quantitative real-time PCR (qRT-PCR) did not show significantly influence in gene expression of gtfB, gtfC or gtfD (P = 0.32, 0.06, 0.44 respectively).ConclusionsArg could reduce the biomass of poly-microbial dental biofilms and S. mutans biofilms, which may be due to the impact of Arg on water-insoluble EPS. Considering the contribution to pH homeostasis in dental biofilms, Arg may serve as an important agent keeping oral biofilms healthy thus prevent dental caries.     

Comparative effect of a stannous fluoride toothpaste and a sodium fluoride toothpaste on a multispecies biofilm

ObjectivesThis paper aimed to compare the mode of action of a stannous fluoride-containing toothpaste with a conventional sodium fluoride-containing toothpaste on anti-biofilm properties.MethodsA three-species biofilm model that consists of Streptococcus mutans, Streptococcus sanguinis and Porphyromonas gingivalis was established to compare the anti-biofilm properties of a stannous fluoride-containing toothpaste (CPH), a conventional sodium fluoride-containing toothpaste (CCP) and a negative control (PBS). The 48 h biofilms were subjected to two-minute episodes of treatment with test agents twice a day for 5 consecutive days. Crystal violet staining and XTT assays were used to evaluate the biomass and viability of the treated biofilm. Live/dead staining and bacteria/extracellular polysaccharides (EPS) double-staining were used to visualize the biofilm structure and to quantify microbial/extracellular components of the treated biofilms. Species-specific fluorescent in situ hybridization and quantitative polymerase chain reaction (qPCR) were used to analyze microbial composition of the biofilms after treatment.ResultsThe biomass and viability of the biofilms were significantly reduced after CPH toothpaste treatment. The inhibitory effect was further confirmed by the live/dead staining. The EPS amounts of the three-species biofilm were significantly reduced by CCP and CPH treatments, and CPH toothpaste demonstrated significant inhibition on EPS production. More importantly, CPH toothpaste significantly suppressed S. mutans and P. gingvalis, and enriched S. sanguinis in the three-species biofilm. In all experiments CPH had a significantly greater effect than CCP (p < 0.05) and CCP had a greater effect than PBS (p < 0.05).ConclusionsStannous fluoride-containing toothpaste not only showed better inhibitory effect against oral microbial biofilm, but was also able to modulate microbial composition within multi-species biofilm compared with conventional sodium fluoride-containing toothpaste.     

Antimicrobial activity of nanoemulsion on cariogenic Streptococcus mutans

Objective

To assess antimicrobial activities of nanoemulsion (NE) to control the adhesion and biofilm formation by Streptococcus mutans by in vitro.

Design

In vitro antimicrobial susceptibility of nanoemulsion was determined as per National Committee for Clinical Laboratory Standards guidelines and agar diffusion, serial dilution technique for the determination of minimum inhibitory concentration and minimum bactericidal concentration (MIC/MBC). Efficacy was tested by kinetics of killing, biofilm assay and scanning electron microscopy.

Results

: NE concentrations ranging from 1:100 to 1:10,000 dilutions were effective against S. mutans as shown through MIC/MBC assays. NE showed antimicrobial activity against planktonic cells at high dilutions, confirmed by time kill studies. 4-day-old S. mutans biofilms were treated with NE; subsequent reductions of bacterial cell counts were noticed with decreasing dilutions. Staining of NE-treated biofilms with LIVE/DEAD BacLight resulted in dead cell areas of up to 48% in 1 min, 84% at 1 h and significant (<0.05) increases in dead cell counts at all time points. Damage to cell membranes and cell walls of S. mutans by NE was demonstrated using scanning electron microscopy (SEM).

Conclusion

These results suggest that nanoemulsion has effective antibacterial activity against S. mutans and may be a useful medication in the prevention of dental caries.     

The antimicrobial efficacy of Fructus mume extract on orthodontic bracket: A monospecies-biofilm model study in vitro

Objective

The aim of this study was to evaluate the antimicrobial efficacy of Traditional Chinese Medicine Fructus mume on a monospecies-biofilm model established on orthodontic brackets in vitro.

Materials and methods

The antimicrobial effect of Fructus mume aqueous extract on the planktonic Streptococcus mutans (S. mutans) was tested by microdilution method (MIC). The cell viability of S. mutans biofilm on Damon3 MX bracket (Ormco, USA) after exposed to Fructus mume extract was quantified by XTT reduction assay. Visualization of the samples was performed by fluorescence microscope and confocal laser scanning microscopy (CLSM).

Results

HPLC analysis revealed that the main compounds of Fructus mume are organic acids. The MIC of Fructus mume extract on the planktonic S. mutans was 50 mg/mL. The optical density (OD) values, measured by XTT reduction assay from S. mutans biofilms after 1-min exposure to different test agents, demonstrated that the cell viability of S. mutans biofilms exposed to 250 mg/mL Fructus mume extract < BHI (−) (p < 0.01). Microscope image showed that Fructus mume extract obviously increased the amount of dead bacteria on the surface of bracket.

Conclusion

Fructus mume extract showed antimicrobial effect on S. mutans biofilm on orthodontic bracket in vitro which may indicate its potential use as an oral antimicrobial agent for orthodontic patients.     

Inhibitory effects of fruit berry extracts on Streptococcus mutans biofilms

Dark‐colored fruit berries are a rich source of polyphenols that could provide innovative bioactive molecules as natural weapons against dental caries. High‐quality extracts of cranberry, blueberry, and strawberry, and a combination of the three berry extracts (Orophenol), were used to treat 24‐h‐old Streptococcus mutans biofilms. The grown biofilms were treated with the berry extracts at concentrations ranging from 62.5 to 500 μg ml^?1. Treated biofilms were assessed for metabolic activity, acidogenicity, biovolumes, structural organization, and bacterial viability. The biofilms treated with the cranberry and Orophenol extracts exhibited the most significant reductions in metabolic activity, acid production, and bacterial/exopolysaccharide (EPS) biovolumes, while their structural architecture appeared less compact than the control‐treated biofilms. The blueberry extract produced significant reductions in metabolic activity and acidogenicity only at the highest concentration tested, without significantly affecting bacterial/EPS biovolumes or biofilm architecture. Strawberry extracts had no significant effects on S. mutans biofilms. None of the berry extracts were bactericidal for S. mutans. The results indicate that cranberry extract was the most effective extract in disrupting S. mutans virulence properties without significantly affecting bacterial viability. This suggests a potential ecological role for cranberry phenols as non‐bactericidal agents capable of modulating pathogenicity of cariogenic biofilms.     

Fluoride releasing and enamel demineralization around orthodontic brackets by fluoride-releasing composite containing nanoparticles

Introduction

Fluoride-containing materials have been suggested to control enamel demineralization around orthodontic brackets during the treatment with fixed appliances. The improvement of their properties has been made through innovations, such as the application of nanotechnology by incorporation of nanofillers.

Objective

This in vitro study evaluated the capacity of fluoride releasing and enamel demineralization inhibition of fluoride-releasing nanofilled cement around orthodontic brackets using an artificial caries biofilm model.

Materials and methods

Forty bovine enamel discs were selected by evaluating surface microhardness and randomized into four groups (n?=?10): non-fluoride-releasing microfilled composite, fluoride-releasing microfilled composite, resin-modified glass ionomer cement (RMGI), and fluoride-releasing nanofilled composite (FN). After brackets bonding in each disc, the specimens were subjected to a cariogenic challenge through a Streptococcus mutans biofilm model. After the experimental period, the biofilm formed around the brackets was collected for fluoride analysis and the mineral loss around the brackets was determined by integrated demineralization via cross-sectional microhardness measurement at 20 and 70 μm from the bracket margin. Additionally, samples of each group were subjected to energy-dispersive X-ray spectroscopy (EDX) analysis examined under a scanning electron microscopy (SEM). ANOVA followed by Tukey test were applied for fluoride concentration and mineral loss data, respectively.

Results

At both distances, only RMGI statistically differed from the other groups presenting the lowest demineralization, although there was a trend to a lower demineralization of enamel around brackets in FN group. Similar condition was found to fluoride concentration and EDX/SEM analysis.

Conclusions

Under the cariogenic exposure condition of this study, the fluoride-releasing nanofilled material had similar performance to fluoride-releasing microfilled materials.

Clinical relevance

The presence of nanofillers in the fluoride-releasing materials studied did not promote further benefits against caries lesion development around brackets and presented inferior demineralization inhibition than the resin-modified glass ionomer material.     

In vitro study of biofilm formation and effectiveness of antimicrobial treatment on various dental material surfaces

Elevated proportions of Candida albicans in biofilms formed on dentures are associated with stomatitis whereas Streptococcus mutans accumulation on restorative materials can cause secondary caries. Candida albicans, S. mutans, saliva‐derived and C. albicans/saliva‐derived mixed biofilms were grown on different materials including acrylic denture, porcelain, hydroxyapatite (HA), and polystyrene. The resulting biomass was analysed by three‐dimensional image quantification and assessment of colony‐forming units. The efficacy of biofilm treatment with a dissolved denture cleansing tablet (Polident^®) was also evaluated by colony counting. Biofilms formed on HA exhibited the most striking differences in biomass accumulation: biofilms comprising salivary bacteria accrued the highest total biomass whereas C. albicans biofilm formation was greatly reduced on the HA surface compared with other materials, including the acrylic denture surface. These results substantiate clinical findings that acrylic dentures can comprise a reservoir for C. albicans, which renders patients more susceptible to C. albicans infections and stomatitis. Additionally, treatment efficacy of the same type of biofilms varied significantly depending on the surface. Although single‐species biofilms formed on polystyrene surfaces exhibited the highest susceptibility to the treatment, the most surviving cells were recovered from HA surfaces for all types of biofilms tested. This study demonstrates that the nature of a surface influences biofilm characteristics including biomass accumulation and susceptibility to antimicrobial treatments. Such treatments should therefore be evaluated on the surfaces colonized by the target pathogen(s).     

In vitro study of the properties of Streptococcus mutans in starvation conditions

Objectives

The present study is to assess Streptococcus mutans survivability in different starvation conditions and to determine the resistance of starved S. mutans to lethal acid and two common anti-caries agents, sodium fluoride (NaF) and chlorhexidine acetate (CHX).

Methods

S. mutans survival rates in sterile water, PBS, sterile saliva, 1/5 strength BHI and BHI were determined at a given time by plate count of viable cell. The resistance of starved S. mutans and control S. mutans to four times the minimal bactericidal concentration (MBC) of NaF, two times the MBC of CHX and acid (pH 2.8) was evaluated and compared respectively. Furthermore, field emission scanning electron microscope (FE-SEM) was used to observe the morphologic characteristics of the starved S. mutans cells.

Results

S. mutans showed starvation tolerance under five different starvation conditions, but the bacterial survival rates were different at the same time points. The starved S. mutans exhibited significantly higher resistance (p < 0.05) to challenge by anti-caries agents and acid than the control S. mutans. Additionally, starvation resulted in the morphologic modification of S. mutans, and the disruptive degree depended on the change in time.

Conclusion

The present study indicates that S. mutans displays starvation tolerance, and starvation decreased the susceptibility of S. mutans to NaF, CHX and acid.     

Effect of biofilm formation on virulence factor secretion via the general secretory pathway in Streptococcus mutans

Objectives

To investigate the role of SecA in protein secretion, and to evaluate the effect of biofilm formation on protein secretion in Streptococcus mutans.

Design

S. mutans strains UA159 and GS-5 were used in this study. Cells grown in biofilm and planktonic conditions were observed using immunogold electron microscopy. The mRNA levels of ftf, gtfB, gtfC, gtfD, Pac and secA were analysed in different growth conditions using real-time quantitative polymerase chain reaction. The levels of wall proteins and whole-cell protein extracts were examined using Western blot analysis.

Results

A microdomain colocalised with SecA and virulence factors such as Pac (AgI/II) and glucosyltransferase (GTF) was observed. The mRNA level of secA was upregulated in the biofilm condition. The level of protein expression of SecA and wall protein levels of GTF, fructosyltransferase (FTF) and Pac (AgI/II) in the biofilm condition were significantly higher than in the planktonic condition.

Conclusions

These data suggest that S. mutans utilises the Sec pathway to secrete virulence factor proteins such as Pac (AgI/II), GTF and FTF, and protein secretion occurred at a distinct microdomain. The level of SecA, the key factor in the Sec pathway, was influenced significantly by biofilm formation in S. mutans.     

Inhibitory effects of tea catechin epigallocatechin-3-gallate against biofilms formed from Streptococcus mutans and a probiotic lactobacillus strain

ObjectiveEffects of tea catechin epigallocatechin-3-gallate (EGCG) against biofilm formation by Streptococcus mutans and probiotic Lactobacillus casei in Yakult^® (LcY) were examined.DesignBiofilms were formed by S. mutans alone (Sm) and co-culture of S. mutans and LcY (Sm + LcY) in the absence or presence of EGCG. The biomass of biofilms, which were sonicated or not, was measured by the crystal violet assay. Biofilm morphology was observed by scanning electron microscopy. Bacterial viability and extracellular polysaccharides were determined by SYTO9/propidium iodide and dextran-conjugated fluorescein staining, respectively, and confocal microscopy. Gene expression of glucosyltransferase was determined by quantitative polymerase chain reaction.ResultsWhile 250 μg/ml EGCG significantly decreased the biomass and acid production of Sm biofilms, 500 μg/ml EGCG was required to inhibit Sm + LcY biofilm formation and acid production. EGCG decreased the amount of live bacteria present in both Sm and Sm + LcY biofilms. The level of dead bacteria in Sm + LcY biofilms was higher than in Sm biofilms when formed in the presence of 250 μg/ml EGCG. EGCG decreased levels of extracellular polysaccharides in Sm and Sm + LcY biofilms. The extent of biofilm removal by sonication was not different between Sm and Sm+LcY biofilms formed in the absence or presence of 62.5 or 125 μg/ml EGCG. The level of Sm gtfB and gtfD expression in Sm + LcY biofilms was higher than those in the Sm biofilms when formed in the presence of EGCG at 250 μg/ml.ConclusionThe results indicated that LcY might interfere the inhibitory effects of EGCG against biofilm formation by S. mutans.     

Clotrimazole and econazole inhibit Streptococcus mutans biofilm and virulence in vitro

Objective: The aim of this study was to determine the inhibitory effect of eight antifungal drugs on S. mutans growth, biofilm formation and virulence factors.MethodsThe actions of antifungal drugs on S. mutans were determined by recovery plates and survival kinetic curves. Biofilms were observed by scanning electron microscopy and the viable cells were recovered on BHI plates, meanwhile biofilms were stained by BacLight live/dead kit to investigate the biofilm viability. Bacteria/extracellular polysaccharides staining assays were performed to determine the EPS production of S. mutans biofilms. Acidogenicity and acidurity of S. mutans were determined using pH drop and acid tolerance assays, and the expression of ldh gene was evaluated using qPCR.ResultsWe found that clotrimazole (CTR) and econazole (ECO) showed antibacterial activities on S. mutans UA159 and S. mutans clinical isolates at 12.5 and 25 mg/L, respectively. CTR and ECO could also inhibit S. mutans biofilm formation and reduce the viability of preformed biofilm. CTR and ECO affected the live/dead ratio and the EPS/bacteria ratio of S. mutans biofilms. CTR and ECO also inhibited the pH drop, lactate acid production, and acid tolerance. The abilities of CTR and ECO to inhibit S. mutans ldh expression were also confirmed.ConclusionsWe found that two antifungal azoles, CTR and ECO, had the abilities to inhibit the growth and biofilm formation of S. mutans and more importantly, they could also inhibit the virulence factors of S. mutans.     

Application of an active attachment model as a high-throughput demineralization biofilm model

Objectives

To investigate the potential of an active attachment biofilm model as a high-throughput demineralization biofilm model for the evaluation of caries-preventive agents.

Methods

Streptococcus mutans UA159 biofilms were grown on bovine dentine discs in a high-throughput active attachment model. Biofilms were first formed in a medium with high buffer capacity for 24 h and then subjected to various photodynamic therapies (PACT) using the combination of Light Emitting Diodes (LEDs, Biotable^®) and Photogem^®. Viability of the biofilms was evaluated by plate counts. To investigate treatment effects on dentine lesion formation, the treated biofilms were grown in a medium with low buffer capacity for an additional 24 h. Integrated mineral loss (IML) and lesion depth (LD) were assessed by transversal microradiography. Calcium release in the biofilm medium was measured by atomic absorption spectroscopy.

Results

Compared to the water treated control group, significant reduction in viability of S. mutans biofilms was observed when the combination of LEDs and Photogem^® was applied. LEDs or Photogem^® only did not result in biofilm viability changes. Similar outcomes were also found for dentine lesion formation. Significant lower IML and LD values were only found in the group subjected to the combined treatment of LEDs and Photogem^®. There was a good correlation between the calcium release data and the IML or LD values.

Conclusions

The high-throughput active attachment biofilm model is applicable for evaluating novel caries-preventive agents on both biofilm and demineralization inhibition. PACT had a killing effect on 24 h S. mutans biofilms and could inhibit the demineralization process.     

Effects of periodic fluoride treatment on fluoride ion release from fresh orthodontic adhesives

Objective

Periodic fluoride treatment may contribute to the ability of fresh orthodontic adhesives to provide long-term F⁻ release. The effects of periodic fluoride treatment on the amount of F⁻ release from fresh orthodontic adhesives was investigated.

Methods

F⁻ release was measured from a nonfluoride-releasing composite, a fluoride-releasing composite, a polyacid-modified composite (compomer), and two resin-modified glass-ionomer cements (RMGICs) at 1, 2, and 5 days after one of the following treatments: 225 ppm F⁻ solution, 900 ppm F⁻ solution, acidulated phosphate fluoride gel (APF), fluoridated dentifrice, and deionised water (control). F⁻ release was measured in a 5-day cycle, which was repeated 9 consecutive times. The amount of F⁻ release for each group was analysed using the repeated measures analysis of variance. Statistical significance was set at a level of α = 0.05.

Results

Periodic fluoride treatment temporarily increased F⁻ release in fresh fluoride-releasing orthodontic adhesives, but not in fresh nonfluoride-releasing composite. The order of effective fluoride-release was RMGICs > compomer > fluoride-releasing composite > nonfluoride-releasing composite. The application of APF or 900 ppm F⁻ solution was the most effective way to maintain F⁻ release from fresh orthodontic adhesives. However, the amount of F⁻ release gradually decreased with increasing specimen age.

Conclusion

Given the difficulty of routine use of APF at home, the results of this study show that a combination of RMGICs and high-dose fluoride mouth rinse is the most effective protocol to maintain F⁻ release from fresh orthodontic adhesives.

Clinical significance

Most studies have investigated fluoride-uptake abilities using aged materials in which fluoride had been lost for at least 1 month. This study has found that periodic fluoride treatment altered the conventional F⁻ release pattern of fresh fluoride-releasing materials and type of fluoride-containing medium plays a more critical role in fluoride recharging of the materials than fluoride concentration. This study will help clinicians to find the most effective fluoride treatment protocol of fresh materials.     

The effect of delmopinol and fluoride on acid adaptation and acid production in dental plaque biofilms

Objective

To investigate the effect of delmopinol and fluoride alone or in combination on acid adaptation and acid production in plaque biofilm bacteria in vitro.

Design

The effect of delmopinol and fluoride on acid adaptation was tested by exposing the biofilm bacteria, grown in a mini-flow cell system under static conditions, to pH 5.5 overnight in the presence of 0.16 mM delmopinol, 1 mF NaF or a combination of both. The following day, acid adaptation was evaluated by exposing the cells to an acid challenge for 2 h at a pH known to kill non-adapted cells (pH 2.5). The cells were stained using LIVE/DEAD^® BacLight™ Viability stain and the number of viable (acid tolerant) cells was determined using confocal scanning laser microscopy. Control cells were treated in the same manner but without the exposure to delmopinol or fluoride. How delmopinol and fluoride affected acid production was assessed by measuring the pH-drop after glucose pulsing in the presence of delmopinol and/or different concentrations of fluoride.

Results

Fluoride alone or in combination with delmopinol affected the acid adaptation and significantly reduced the acid tolerance of the plaque biofilm. This effect was more pronounced when the two compounds were combined. Delmopinol alone did not affect acid adaptation. A combination of delmopinol and fluoride also reduced acid production at concentrations where neither of the compounds in isolation had an effect.

Conclusion

Fluoride and delmopinol can work synergistically to affect acid adaptation and acid production in plaque biofilm bacteria.     

Effect of sodium fluoride on oral biofilm microbiota and enamel demineralization

ObjectiveFluoride is widely used as an anti-caries agent, e.g. in toothpastes and mouth rinses. However, the nature of the anti-caries action is not entirely clear. Mechanisms suspected to explain the cariostatic effect include inhibitory effects on acid formation by bacteria, inhibition of extracellular polysaccharide (EPS) production, inhibition of enamel demineralization and enhancement of remineralizaton or combination thereof. The aim of this study was to examine with the supragingival Zurich in vitro biofilm model the effect of fluoride in NaF formulation, on the microbiota and on demineralization.MethodsBiofilms consisting of Actinomyces oris, Candida albicans, Fusobacterium nucleatum, Streptococcus oralis, Veillonella dispar and Streptococcus sobrinus, were grown anaerobically on sintered hydroxyapatite or bovine enamel disks, exposed to 200, 400, and 1400 ppm of NaF, or 0.1% chlorhexidine (positive control). The biofilms were harvested after 64 h and CFUs were assessed for total bacteria. Demineralization of enamel disks was measured by quantitative light-induced fluorescence.ResultsNaF did not affect the bacterial numbers. No enamel mineral loss was observed at 1400 and 400 ppm of fluoride, whereas the pH of the surrounding medium was increased to 5.5 and 5.0, respectively, compared to the untreated control (pH 4.5 and mineral loss ΔF of −32%). At 1400 ppm NaF the biofilm’s EPS volume was also significantly reduced.ConclusionsAdministration of NaF completely prevented demineralization without affecting biofilm composition and growth. This protective effect may be attributed to the observed decrease in acid production or EPS volume, or to a shift in the de/remineralization balance.