Cariostatic Mechanisms of Fluorides: Clinical Observations

Sy, Ericsson

doi:10.1159/000260293

Cited by 85 publications

(43 citation statements)

References 60 publications

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“…Plaque pH varies from near neutral values in the resting state (no fermentable substrates available) to well below pH 5 during periods of exposure to fermentable substrates (15). Fluoride is a well-known cariostatic agent which is responsible for a major reduction in the prevalence of dental caries (2,12). The principal cariostatic effect of fluoride is considered to depend on its incorporation into the enamel crystal structure with a resulting decrease in acid susceptibility of the tooth mineral (14).…”

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confidence: 99%

Role of the cell membrane in pH-dependent fluoride inhibition of glucose uptake by Streptococcus mutans

Germaine¹,

Tellefson²

1986

Antimicrob Agents Chemother

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The effect of pH on the fluoride sensitivity of glucose uptake by whole cells and glucose transport by permeabilized cells of Streptococcus mutans was compared. Whole cells exhibited a marked pH-dependent sensitivity to fluoride over the pH range 7.0 to 5.0. As the pH was decreased, fluoride sensitivity increased. In contrast, no significant effect of pH on the fluoride sensitivity of glucose transport (e.g., phosphorylation) by permeabilized cells energized with 2-phosphoglycerate was noted. The relative effect of pH on the fluoride sensitivity of whole cell glucose uptake and fermentation was similar. These data are consistent with the notion that the cell membrane is impermeable to the fluoride anion and that intracellular accumulation of fluoride depends on translocation of hydrogen fluoride across the membrane.Streptococcus mutans is a colonizer of the human tooth surface and is associated with the development of dental caries in humans (5,6,15). This organism is noted for its aciduric, as well as its acidogenic, properties relative to those of other common plaque microorganisms (8,9,15). Development of dental caries is thought to depend on the acid demineralization of tooth enamel as a direct result of the acidic fermentative activities of S. mutans and other plaque microbes (15). Plaque pH varies from near neutral values in the resting state (no fermentable substrates available) to well below pH 5 during periods of exposure to fermentable substrates (15). Fluoride is a well-known cariostatic agent which is responsible for a major reduction in the prevalence of dental caries (2, 12). The principal cariostatic effect of fluoride is considered to depend on its incorporation into the enamel crystal structure with a resulting decrease in acid susceptibility of the tooth mineral (14). Fluoride also has inhibitory effects on numerous enzymes (17) and on the fermentative activities and viability of oral microbes, including S. mutans (for reviews, see references 7, 11, 13, and 16). The fluoride sensitivity of S. mutans sugar fermentation and growth is generally increased as the pH is decreased (1,7,11,16). It has been suggested that the pH-dependent nature of fluoride sensitivity is based on the passive permeability of the cell membrane to HF and impermeability to fluoride anion (16). As the pH of the environment is decreased, the absolute concentration of HF is increased (pK, -3.45) and the pH difference across the cell membrane promotes accumulation of fluoride into the more alkaline cell cytoplasm. This model is supported by the observation that the intracellular accumulation of fluoride increases with the magnitude of the pH difference across the cell membrane of S. mutans (16). In light of these observations, we chose to investigate the role of the cell membrane in the pH sensitivity of fluoride inhibition of glucose uptake and transport by S. mutans over the pH range commonly encountered in plaque. If the model described above is correct, whole cell glucose uptake, but not glucose transport by permeabilized ...

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Role of the cell membrane in pH-dependent fluoride inhibition of glucose uptake by Streptococcus mutans

Germaine¹,

Tellefson²

1986

Antimicrob Agents Chemother

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“…The effec tiveness of fluoride has been established in both man [Ericsson, 1977] and experi mental animals [Larson, 1977], whereas the evidence for organic phosphates rests large ly on animal experimentation [Harris, 1970;Grenby, 1975Grenby, ,1977.…”

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Use of High-Performance Liquid Chromatography Techniques to Study the Protection of Hydroxylapatite by Fluoride and Glycerophosphate against Demineralization in vitro

Grenby¹,

Bull²

1980

Caries Res

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Apparatus and techniques were evolved for a sensitive and reproducible test measuring the demineralization by acid of hydroxylapatite or powdered enamel as the stationary phase in high-performance liquid chromatography columns. Demineralization was quantified by monitoring the column eluate for UV absorbance and integration of the area of the UV peaks, with concomitant serial calcium analyses. Treating the hydroxylapatite with sodium fluoride conferred relatively long-acting protection against demineralization. The main effect of the fluoride appeared to be in reducing the acid solubility of the outer layers of the hydroxylapatite. Contrary to earlier theories that the protective action of calcium glycerophosphate was exerted only in the media surrounding the teeth, this agent was found to interact directly with hydroxylapatite, reducing the extent of demineralization by an average of 50%. The UV and the calcium analysis data showed how the mechanisms of protection by glycerophosphates and fluoride differed.

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“…Studies by Loesche et al (16,17) have shown that daily applications of APF gels (12,300 ,ug of fluoride per ml at pH 3.2) significantly reduced proportions of S. mutans after 6 and 12 weeks posttreatment compared with pretreatment levels. Although it was speculated that a bactericidal effect might be responsible for the observed reductions (15), other mechanisms of suppression besides bactericidal action might be involved (6). In fact, reductions in proportions of S. mutans were greater at the 6-and 12-week intervals than at the 1-week posttreatment interval, suggesting that an immediate bactericidal effect on S. mutans did not occur.…”

Section: Resultsmentioning

confidence: 99%

pH-dependent bactericidal effects of acidulated fluoride gels on preformed plaque aggregates of Streptococcus mutans 6715

Caufield¹,

Wannemuehler²

1984

Antimicrob Agents Chemother

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The anticaries action of topically applied sodium fluoride (NaF) preparations has been attributed, at least in part, to the antibacterial effect of fluoride on cariogenic bacteria. In this report we examined the bactericidal activity of acidulated NaF gels against preformed plaque aggregates of Streptococcus mutans 6715. Both commercially available and laboratory-prepared gels were tested. Prepared NaF gels were acidified to various pH levels with HCI, H3PO4, or HF. The aggregates of S. mutans were immersed in the various fluoride gels for 5 min and then monitored for viability. None of the commercially available NaF gels with pHs of 3.5 to 4.5 and fluoride concentrations of 5,000 to 12,300 ,ug/ml were capable of exerting complete bactericidal activity against aggregates of S. mutans. For the laboratory-prepared NaF gels, neither the source of hydrogen ion nor the source of fluoride influenced the outcome when fluoride was present at the appropriate MBC and pH. NaF gels with a fluoride concentration of 37,000 ,ug/ml were bactericidal to S. mutans at pH 3.0. At pH 2.5 and 2.0, approximately 12,000 and 1,100 ,ug of fluoride per ml, respectively, was bactericidal. Results from this study suggest that the bactericidal properties of acidulated NaF gels can be enhanced by lowering their pHs to below 3.0.Frequent and infrequent topical applications of high concentrations of fluoride (>1,000 ,ug/ml) inhibit dental caries (for review, see reference 6). The exact mechanism(s) responsible for this inhibition, however, remains unclear. Several studies have reported reductions in proportions of cariogenic bacteria such as Streptococcus mutans for various intervals after topical fluoride applications, suggesting that fluoride, when present in these high concentrations, might exert marked inhibitory and even bactericidal effects on these bacteria (2,16,17, 26).Attempts have been made to examine the antibacterial properties of fluoride on cariogenic bacteria with various in vitro assays. For example, broth dilution (2,4,8,18) and pellet culture (19) assays clearly indicate that fluoride is capable of exerting both inhibitory and bactericidal effects on strains of S. mutans, depending upon the concentrations of the organisms and fluoride, duration of exposure, and pH of the medium, among other factors. Unfortunately, these conventional in vitro methods tend to greatly overestimate the antimicrobial potency of fluoride when compared with what can be expected in vivo when factors such as density of the microbial mass colonizing the teeth, accessibility of the agent to various tooth surfaces, and duration and frequency of applications are considered (24). More specifically, conventional assays involve exposing dispersed bacterial suspensions to antimicrobial agents for prolonged periods (i.e., 18 to 48 h) and usually in the presence of nutrient medium, which can inactivate or adversely affect the properties of the antimicrobial agent. Consequently, extrapolating from these observations to predict what will occur in vivo can be misl...

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Cariostatic Mechanisms of Fluorides: Clinical Observations

Cited by 85 publications

References 60 publications

Role of the cell membrane in pH-dependent fluoride inhibition of glucose uptake by Streptococcus mutans

Role of the cell membrane in pH-dependent fluoride inhibition of glucose uptake by Streptococcus mutans

Use of High-Performance Liquid Chromatography Techniques to Study the Protection of Hydroxylapatite by Fluoride and Glycerophosphate against Demineralization in vitro

pH-dependent bactericidal effects of acidulated fluoride gels on preformed plaque aggregates of Streptococcus mutans 6715

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