Effects of Sodium Trimetaphosphate, Associated or Not with Fluoride, on the Composition and pH of Mixed Biofilms, before and after Exposure to Sucrose

Dual-species biofilm of Streptococcus mutans and Candida albicans produces subsurface caries lesions on bovine enamel

OBJECTIVES

To develop a protocol for forming subsurface caries lesions on bovine enamel by dual-species biofilms of Streptococcus mutans and Candida albicans in vitro.

DESIGN

Biofilms were grown on bovine enamel specimens in artificial saliva (AS) for seven days. After 24 h of formation, the AS was supplemented or not with fluoride (F) using sodium fluoride (0.005 or 0.008 ppm F), and the biofilms were exposed or not to a 20 % sucrose solution (reproducing a cariogenic challenge) once/day. On the seventh day, the biofilms were harvested and had their extracellular polysaccharides (EPS) and inorganic components analyzed. The specimens were subjected to computed X-ray microtomography analysis to determine their mineral concentration. Data were compared using two-way analyses of variance, followed by Fisher's LSD or Student-Newman-Keuls tests (p < 0.05).

RESULTS

Biofilms exposed to the cariogenic challenge had significantly higher EPS concentrations than those not exposed, regardless of the presence of F. For biofilms grown with 0.008 ppm F, those exposed to the cariogenic challenge had lower F levels than those not exposed. For biofilms exposed to the cariogenic challenge, those grown with 0.008 ppm F had lower lesion depths and integrated mineral loss, and higher outer layers than those grown without F.

CONCLUSIONS

The dual biofilm model assessed was able to create subsurface caries lesions in bovine enamel in vitro, which was influenced by the presence of F in the culture medium and exposure to sucrose.

Evaluation of Solutions Containing Fluoride, Sodium Trimetaphosphate, Xylitol, and Erythritol, Alone or in Different Associations, on Dual-Species Biofilms

Although the association of polyols/polyphosphates/fluoride has been demonstrated to promote remarkable effects on dental enamel, little is known on their combined effects on biofilms. This study assessed the effects of solutions containing fluoride/sodium trimetaphosphate (TMP)/xylitol/erythritol on dual-species biofilms of Streptococcus mutans and Candida albicans. Biofilms were grown in the continuous presence of these actives alone or in different associations. Quantification of viable plate counts, metabolic activity, biofilm biomass, and extracellular matrix components were evaluated. Overall, fluoride and TMP were the main actives that significantly influenced most of the variables analyzed, with a synergistic effect between them for S. mutans CFUs, biofilm biomass, and protein content of the extracellular matrix (p < 0.05). A similar trend was observed for biofilm metabolic activity and carbohydrate concentrations of the extracellular matrix, although without statistical significance. Regarding the polyols, despite their modest effects on most of the parameters analyzed when administered alone, their co-administration with fluoride and TMP led to a greater reduction in S. mutans CFUs and biofilm biomass compared with fluoride alone at the same concentration. It can be concluded that fluoride and TMP act synergistically on important biofilm parameters, and their co-administration with xylitol/erythritol significantly impacts S. mutans CFUs and biomass reduction.

Antimicrobial Effect of Low-Fluoride Toothpastes Containing Polyphosphate and Polyols: An In Vitro Assessment of Inhibition Zones

This study evaluated the antimicrobial effect of toothpastes containing 200 ppm fluoride (200F), xylitol (X, 16%), erythritol (E, 4%), and sodium trimetaphosphate (TMP, 0.25%), alone or in different associations, against Streptococcus mutans (SM), Lactobacillus casei (LC), Actinomyces israelii (AI), and Candida albicans (CA). Suspensions of the micro-organisms were added to a BHI Agar medium. Five wells were made on each plate to receive toothpaste suspensions at different dilutions. Toothpastes containing no actives (placebo) or 1100 ppm F (1100F) were used as negative and positive controls. Two-way ANOVA and Tukey's HDS test were used (p < 0.05). For SM, the largest halo was for 200F+TMP at all dilutions, followed by the 200F+X+E toothpaste (p < 0.001). For LC, the overall trend showed that the polyols effectively inhibited microbial growth, and the association with the other compounds enhanced such effects (p < 0.001). For AI, a less-defined trend was observed. For CA, the experimental toothpaste (200F+X+E+TMP) was consistently more effective than the other treatments, followed by 200F+X+E (p < 0.001). The association of polyols and TMP in a low-fluoride toothpaste effectively reduced the growth of cariogenic micro-organisms (SM, CA, and LC), suggesting that this formulation could be an interesting alternative for children due to its low fluoride content.

Activity of Sodium Trimetaphosphate Nanoparticles on Cariogenic-Related Biofilms In Vitro

In light of the promising effect of sodium trimetaphosphate nanoparticles (TMPn) on dental enamel, in addition to the scarce evidence of the effects of these nanoparticles on biofilms, this study evaluated the activity of TMPn with/without fluoride (F) on the pH, inorganic composition and extracellular matrix (ECM) components of dual-species biofilms of Streptococcus mutans and Candida albicans. The biofilms were cultivated in artificial saliva in microtiter plates and treated with solutions containing 1% or 3% conventional/microparticulate TMP (TMPm) or TMPn, with or without F. After the last treatment, the protein and carbohydrate content of the ECM was analyzed, and the pH and F, calcium (Ca), phosphorus (P), and TMP concentrations of the biofilms were determined. In another set of experiments, after the last treatment, the biofilms were exposed to a 20% sucrose solution, and their matrix composition, pH, and inorganic component contents were evaluated. 3% TMPn/F significantly reduced ECM carbohydrate and increased biofilm pH (after sucrose exposure) than other treatments. Also, it significantly increased P and F levels before sucrose exposure in comparison to 3% TMPm/F. In conclusion, 3% TMPn/F affected the biofilm ECM and pH, besides influencing inorganic biofilm composition by increasing P and F levels in the biofilm fluid.

Effects of Sodium Hexametaphosphate and Fluoride on the pH and Inorganic Components of Streptococcus mutans and Candida albicans Biofilm after Sucrose Exposure

In order to improve the anticaries effects of fluoridated products, the supplementation of these products has been considered a promising alternative for caries control. This study evaluated the effects of sodium hexametaphosphate (HMP) and/or fluoride (F) on the inorganic components and pH of Streptococcus mutans and Candida albicans dual-species biofilms. The biofilms were treated 72, 78, and 96 h after the beginning of their formation with 0.25, 0.5, or 1% HMP-containing solutions with or without F (500 ppm, as sodium fluoride). F-containing solutions (500 ppm and 1100 ppm) and artificial saliva were used as controls. The biofilms were exposed to a 20% sucrose solution after the third treatment. Along with the biofilm pH, the concentrations of F, calcium, phosphorus (P), and HMP were determined. HMP, combined with F, increased F levels and decreased P levels in the biofilm fluid compared to that of the solution with 500 ppm F. Exposure to sucrose decreased the concentrations of all ions in the biomass, except for HMP; 1% HMP, combined with F, promoted the highest pH. It can be concluded that HMP affected the inorganic composition of the biofilm and exerted a buffering effect on the biofilm pH.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion

OBJECTIVES

The aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans.

METHODS

Bovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100ppm F, 225ppm F, 100ppm F+0.2%TMP or 100ppm F+0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy.

RESULTS

The nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5-20 μm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log₁₀cm²) and structurally affected the biofilms.

CONCLUSION

The 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans.

CLINICAL SIGNIFICANCE

The focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

Effects of sodium hexametaphosphate microparticles or nanoparticles on the growth of saliva-derived microcosm biofilms

OBJECTIVES

This study evaluated the effects of sodium hexametaphosphate microparticles (HMPmicro) or nanoparticles (HMPnano) on the growth of saliva-derived microcosm biofilms MATERIALS AND METHODS: Saliva-derived biofilms were formed on glass coverslips for 24 h. Thereafter, Streptococcus mutans (C180-2) was incorporated or not into the biofilms. From that time point onwards, solutions containing 0.2% HMPmicro or HMPnano, combined or not with 220 ppm F, were constantly present in the culture medium. In addition, 220 ppm F alone (220F) and McBain medium without any compound were also tested as positive and negative controls (CTL), respectively. After 96 h, the biofilms were plated on anaerobic blood agar or sucrose agar bacitracin for total and S. mutans CFU-counting, respectively. Biofilms' lactic acid production was analysed spectrophotometrically. Data were submitted to ANOVA or Kruskal-Wallis' tests, followed by Student-Newman-Keuls' test (p<0.05; n=12).

RESULTS

HMPmicro or HMPnano led to significantly lower lactic acid production, and significant reductions in total CFU-counting in microcosm biofilms, supplemented or not with S. mutans, in comparison to both controls, with significant differences between 220F and CTL. No significant differences were observed among the groups treated with HMPmicro or HMPnano (with or without F). The same trend was seen for S. mutans CFU-counting, in biofilms supplemented with S. mutans.

CONCLUSIONS

HMP significantly reduced total and S. mutans CFU counts, as well as lactic acid production by saliva-derived microcosm biofilms.

CLINICAL RELEVANCE

These findings in saliva-derived microcosm biofilms suggest that HMP stands as a promising alternative for the control of cariogenic biofilms.

In it together: Candida-bacterial oral biofilms and therapeutic strategies

Under natural environmental settings or in the human body, the majority of microorganisms exist in complex polymicrobial biofilms adhered to abiotic and biotic surfaces. These microorganisms exhibit symbiotic, mutualistic, synergistic, or antagonistic relationships with other species during biofilm colonization and development. These polymicrobial interactions are heterogeneous, complex and hard to control, thereby often yielding worse outcomes than monospecies infections. Concerning fungi, Candida spp., in particular, Candida albicans is often detected with various bacterial species in oral biofilms. These Candida-bacterial interactions may induce the transition of C. albicans from commensal to pathobiont or dysbiotic organism. Consequently, Candida-bacterial interactions are largely associated with various oral diseases, including dental caries, denture stomatitis, periodontitis, peri-implantitis, and oral cancer. Given the severity of oral diseases caused by cross-kingdom consortia that develop hard-to-remove and highly drug-resistant biofilms, fundamental research is warranted to strategically develop cost-effective and safe therapies to prevent and treat cross-kingdom interactions and subsequent biofilm development. While studies have shed some light, targeting fungal-involved polymicrobial biofilms has been limited. This mini-review outlines the key features of Candida-bacterial interactions and their impact on various oral diseases. In addition, current knowledge on therapeutic strategies to target Candida-bacterial polymicrobial biofilms is discussed.

Calcium glycerophosphate and fluoride affect the pH and inorganic composition of dual-species biofilms of Streptococcus mutans and Candida albicans

OBJECTIVES

This study evaluated the influence of calcium glycerophosphate (CaGP), combined with or without fluoride (F), on the pH and concentrations of F, Ca, and P of dual-species biofilms of Streptococcus mutans and Candida albicans, with or without exposure to sucrose.

METHODS

The biofilms (n = 9) received three treatments (72, 78, and 96 h after the start of their formation) at three CaGP concentrations (0.125, 0.25, or 0.5%), with or without F at 500 ppm (as NaF). Solutions containing 500 and 1100 ppm F and artificial saliva were also tested as controls. Biofilm pH was measured, and the concentrations of F, Ca, P, and CaGP were determined (solid and fluid phases). In a parallel experiment, after the third treatment, the treated biofilms were exposed to a sucrose solution, and the pH of the medium, F, Ca, P, and CaGP was determined. Data were subjected to two-way ANOVA, followed by Fisher's LSD test (p < 0.05).

RESULTS

Treatment with CaGP and 500 ppm F led to the highest pH values and F and Ca concentrations in the biofilm biomass, both with and without sucrose exposure. CaGP without F led to higher Ca and P concentrations in the biofilm fluid.

CONCLUSIONS

CaGP increased F, Ca, and P concentrations in the biofilm, and its presence promoted an increase in the pH of the medium, even after exposure to sucrose.

CLINICAL SIGNIFICANCE

The present results elucidate the mechanism by which CaGP and F act on biofilms, further interfering with dental caries dynamics.