fluorapatite and Dental-Plaque

Current models for increasing the anti-caries effects of fluoride (F) agents emphasize the importance of maintaining a cariostatic concentration of F in oral fluids. The concentration of F in oral fluids is maintained by the release of this ion from bioavailable reservoirs on the teeth, oral mucosa and - most importantly, because of its association with the caries process - dental plaque. Oral F reservoirs appear to be of two types: (1) mineral reservoirs, in particular calcium fluoride or phosphate-contaminated 'calcium-fluoride-like' deposits; (2) biological reservoirs, in particular (with regard to dental plaque) F held to bacteria or bacterial fragments via calcium-fluoride bonds. The fact that all these reservoirs are mediated by calcium implies that their formation is limited by the low concentration of calcium in oral fluids. By using novel procedures which overcome this limitation, the formation of these F reservoirs after topical F application can be greatly increased. Although these increases are associated with substantive increases in salivary and plaque fluid F, and hence a potential increase in cariostatic effect, it is unclear if such changes are related to the increases in the amount of these reservoirs, or changes in the types of F deposits formed. New techniques have been developed for identifying and quantifying these deposits which should prove useful in developing agents that enhance formation of oral F reservoirs with optimum F release characteristics. Such research offers the prospect of decreasing the F content of topical agents while simultaneously increasing their cariostatic effect.

Topics: Apatites; Bacteria; Biological Availability; Calcium Fluoride; Cariostatic Agents; Dental Plaque; Fluorides; Humans; Mouth; Mouth Mucosa; Saliva; Tooth

Dental caries is a complex disease process that afflicts a large proportion of the world's population, regardless of gender, age and ethnicity, although it does tend to affect more indivduals with a low socioeconomic status to a greater extent. The physicochemical properties of the mineral comprising the tooth surface and subsurface modulate the development, arrestment and remineralization of dental caries. Post-eruption maturation of enamel surfaces and exposed root surfaces is important in order for more susceptible mineral phases to be modified by incorporation of soluble fluoride from the plaque into dental hydroxyapatite. The chemical reactions that occur during acidic conditions when tooth mineral dissolves (critical pH) are determined by the supersaturation of calcium and phosphate within plaque and saliva, as well as if fluoride is present.

Topics: Apatites; Dental Caries; Dental Enamel; Dental Enamel Permeability; Dental Enamel Solubility; Dental Plaque; Durapatite; Humans; Hydrogen-Ion Concentration; Tooth Demineralization; Tooth Remineralization

Because dentin is more caries-susceptible than enamel, its demineralization may be more influenced by additional fluoride (F). We hypothesized that a combination of professional F, applied as acidulated phosphate F (APF), and use of 1100-ppm-F dentifrice would provide additional protection for dentin compared with 1100-ppm-F alone. Twelve adult volunteers wore palatal appliances containing root dentin slabs, which were subjected, during 4 experimental phases of 7 days each, to biofilm accumulation and sucrose exposure 8x/day. The volunteers were randomly assigned to the following treatments: placebo dentifrice (PD), 1100-ppm-F dentifrice (FD), APF + PD, and APF+FD. APF gel (1.23% F) was applied to the slabs once at the beginning of the experimental phase, and the dentifrices were used 3x/day. APF and FD increased F concentration in biofilm fluid and reduced root dentin demineralization, presenting an additive effect. Analysis of the data suggests that the combination of APF gel application and daily regular use of 1100-ppm-F dentifrice may provide additional protection against root caries compared with the dentifrice alone.

Topics: Acidulated Phosphate Fluoride; Adult; Apatites; Biofilms; Calcium Fluoride; Cariogenic Agents; Cariostatic Agents; Cross-Over Studies; Dental Plaque; Dentifrices; Dentin; Double-Blind Method; Drug Combinations; Fluorides; Gels; Hardness; Humans; Microradiography; Placebos; Sucrose; Time Factors; Tooth Demineralization; Tooth Root; Young Adult

The anticaries effect of professional fluoride (F) application has been attributed to calcium-fluoride-like deposits (CaF(2)) formed on enamel, but this has not been clearly demonstrated. We hypothesized that CaF(2) formed on plaque-free enamel by F application would reduce enamel demineralization due to the increase of F availability in fluid of subsequently formed plaque. We created distinct levels of CaF(2) on enamel to evaluate a dose-response effect. Enamel blocks were mounted in contact with a S. mutans test plaque and used in situ by 10 volunteers. F released to the fluid phase of this substrate ("plaque fluid") was measured before a cariogenic challenge. "Plaque fluid" F concentration was highly correlated to the enamel CaF(2) concentration (r = 0.96, p < 0.001) and to consequent enamel demineralization (r = -0.75, p < 0.001). The results suggest that F released to plaque fluid from CaF(2) formed on enamel may play a significant role in the anticaries effect of professionally applied F agents.

Topics: Acidulated Phosphate Fluoride; Animals; Apatites; Biological Availability; Calcium Fluoride; Cariostatic Agents; Cattle; Cross-Over Studies; Dental Enamel; Dental Plaque; Dose-Response Relationship, Drug; Double-Blind Method; Fluorides, Topical; Hardness; Humans; Tooth Demineralization

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) slows the progression of caries and remineralizes enamel subsurface lesions. The aim of this study was to determine the ability of CPP-ACP to increase the incorporation of fluoride into plaque and to promote enamel remineralization in situ. Randomized, double-blind, cross-over studies involved mouthrinses and dentifrices containing CPP-ACP and fluoride. The mouthrinses were used for 60 sec, three times/day for 5 days, and supragingival plaque was collected and analyzed for F. The dentifrices were rinsed as a water slurry for 60 sec four times/day for 14 days in an in situ model. The addition of 2% CPP-ACP to the 450-ppm-F mouthrinse significantly increased the incorporation of fluoride into plaque. The dentifrice containing 2% CPP-ACP produced a level of remineralization similar to that achieved with a dentifrice containing 2800 ppm F. The dentifrice containing 2% CPP-ACP plus 1100 ppm F was superior to all other formulations.

Topics: Adult; Apatites; Cariostatic Agents; Caseins; Chemistry, Pharmaceutical; Cross-Over Studies; Dental Enamel; Dental Plaque; Dentifrices; Double-Blind Method; Drug Combinations; Electron Probe Microanalysis; Female; Fluorides; Humans; Male; Middle Aged; Mouthwashes; Placebos; Sodium Fluoride; Tooth Remineralization

Topics: Apatites; Cariostatic Agents; Dental Caries; Dental Enamel; Dental Plaque; Dentifrices; Fluoridation; Fluorides; Humans; Hydrogen-Ion Concentration; Saliva; Tooth Demineralization; Tooth Remineralization

This article discusses fluoride-releasing materials, including their caries-inhibiting properties and clinical longevity, as well as provides useful application tips. Based on results from clinical trials, there is growing evidence that fluoride-releasing materials, particularly glass ionomers, reduce the occurrence of recurrent caries. As such, they should be employed-especially in the case of high caries-risk patients-as part of an overall treatment plan for maximum care.

Topics: Apatites; Bacteria; Cariostatic Agents; Compomers; Composite Resins; Dental Caries; Dental Plaque; Dental Restoration Wear; Dental Restoration, Permanent; Fluorides; Glass Ionomer Cements; Humans; Tooth Remineralization

Dental plaque fluid is normally supersaturated with respect to enamel mineral but this may change to a state of undersaturation when plaque pH falls following sugar exposure, placing the adjacent enamel at risk of caries. We have determined the saturation status of the fluid in both resting and fermenting plaque following mineral supplementation. Eleven subjects abstained from oral hygiene and rinsed their mouth 3 times/d for 3 d with a placebo solution or with test solutions designed to enrich plaque with hydroxyapatite or fluorhydroxyapatite. On the morning of day 4, plaque samples were collected before and after exposure to 10% sucrose. Compared to the placebo, use of the test rinses resulted in significantly higher concentrations of Ca, P and F in plaque residue. In plaque fluid, higher post-sucrose Ca2+ free concentrations and saturation levels with respect to enamel mineral and fluorapatite were found after use of the hydroxyapatite rinse compared to the placebo, effects that probably resulted from the release of cell-bound Ca2+ as well as from the dissolution of apatite. Thus, some evidence was obtained that the test mouthrinses can counteract the fall in saturation level found when plaque is exposed briefly to sucrose. Potential long-term benefits of the test mouthrinses deserve further study.

Topics: Acetates; Adult; Aged; Apatites; Calcium; Cariogenic Agents; Dental Caries Susceptibility; Dental Enamel; Dental Plaque; Durapatite; Exudates and Transudates; Fermentation; Fluorides; Humans; Hydrogen-Ion Concentration; Hydroxyapatites; Lactic Acid; Middle Aged; Minerals; Mouthwashes; Phosphates; Placebos; Solubility; Sucrose

The benefits of using fluoride to prevent caries have been known for many years, but a complete understanding of this mechanism is still being researched. The fluoride concentration in the apatitic structure of enamel does not have as significant an effect on reducing caries as a continuous presence of fluoride in the plaque liquid. Concentrated, topical fluoride agents (such as in toothpaste, fluoride mouth rinses, gels, or varnishes) have a different mechanism of fluoride protection than low-concentration applications (such as fluoridated water). In initial caries lesions and plaque, concentrated agents form globules of a calcium fluoride-like material on the enamel surface. This material is fairly insoluble, possibly because it is coated with phosphates or proteins. This mechanism explains how the topical application of a fluoride varnish, two or three times a year, can result in caries reduction.

Topics: Apatites; Calcium Fluoride; Cariostatic Agents; Dental Caries; Dental Enamel; Dental Enamel Solubility; Dental Plaque; Exudates and Transudates; Fluorides; Fluorides, Topical; Humans; Hydrogen-Ion Concentration; Sodium Fluoride; Tooth Demineralization; Tooth Remineralization

Release of F from fluorhydroxyapatite (FHAp) during acid dissolution was studied to validate the use of this mineral as a plaque reservoir of F. FHAp minerals having a wide range of F concentrations were synthesised by aqueous precipitation, and samples repeatedly exposed to 50 mM lactic acid solution, pH 4.5, or similar lactic/acetic/formic acid mixtures, until dissolution was complete. While the Ca/P ratio in solution remained relatively constant and close to the ratio in the solid, the solution F/Ca ratio invariably changed during dissolution. During initial stages the F/Ca solution ratio was lower than in the solid but rose to reach a plateau higher than in the solid as dissolution progressed, an effect that was more pronounced with low-F FHAp. With these minerals the plateau F/Ca level never reached 0.2, suggesting that a F-enriched FHAp rather than pure fluorapatite precipitates during dissolution. It is concluded that a high-F FHAp mineral would best serve as an apatitic plaque reservoir of F.

Topics: Acetates; Acids; Apatites; Calcium; Chemical Precipitation; Dental Plaque; Fluorides; Formates; Humans; Hydroxyapatites; Hydroxyl Radical; Lactates; Lactic Acid; Phosphorus; Solubility

Mouthrinses containing zinc ions inhibit plaque acidogenicity, but the effect is transient. Zinc-containing apatite or zinc phosphate precipitated within dental plaque might serve as a reservoir for zinc ions, thus providing prolonged inhibition of acid formation. Zinc-containing fluorhydroxyapatite was prepared from solutions containing CaCl2, KH2PO4, NaF and increasing amounts of ZnCl2 (0.0, 0.005, 0.02, 0.1, 0.2 or 1 mM; minerals No. 1-6, respectively) by raising the pH with ammonia. Zinc phosphate tetrahydrate (mineral No. 7) was prepared in a similar manner from a solution containing ZnCl2 and KH2PO4 only. Dense cell suspensions of Streptococcus mutans NCTC 10449 were incubated with 14C-glucose and one of the test minerals (No. 1-7). Glycolysis was allowed to proceed, with or without pH control, in a pH-stat. Samples were withdrawn at 1, 2, and 3 min, and extracellular glycolytic metabolites were identified by HPLC. Mineral No. 7 inhibited glycolysis and any pH fall almost completely. With the pH fixed at 5.5, reduction of glucose consumption and lactate formation was 83 and 93%, respectively, compared to the no-zinc control mineral (No. 1). No changes in glucose consumption or lactate formation were evident in the presence of minerals No. 2-6. All apatitic minerals had a buffering effect and, in the absence of pH control, glycolysis was increased due to the higher pH. Detectable levels of fluoride were not released by any mineral into the incubation mixture, and zinc only by minerals No. 6 and 7 in greater than trace amounts.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acids; Ammonia; Apatites; Buffers; Calcium; Calcium Phosphates; Carbon Radioisotopes; Chlorides; Chromatography, High Pressure Liquid; Dental Plaque; Glucose; Glycolysis; Hydrogen-Ion Concentration; Lactates; Phosphates; Streptococcus mutans; Zinc; Zinc Compounds

The cariostatic effect of fluoride at different levels of pH in the plaque fluid is discussed. At the pH level 5.5 to 4.5 the plaque fluid is undersaturated with respect to hydroxyapatite and supersaturated with respect to fluorapatite (3). The hydroxyapatite of the enamel then dissolves. With fluoride present in the liquid phase a fluoridated apatite is precipitated in the surface zone of the lesion. In acidic, old plaque the plaque fluid is very likely undersaturated also with respect to fluorapatite (pH less than 4.5) (11). When the liquid phase is undersaturated with respect to fluorapatite no redeposition of mineral lost can occur. In due time an erosion will develop. It is speculated that one reason for the minor effect of fluoride in some caries active patients and in fissures as well is that the plaque fluid is undersaturated with respect to fluorapatite for extended periods.

Topics: Apatites; Dental Caries; Dental Enamel; Dental Enamel Solubility; Dental Plaque; Durapatite; Fluorides; Humans; Hydrogen-Ion Concentration; Hydroxyapatites

The inhibitory effect of fluorapatite (FAP)-derived fluoride upon resting cell suspensions of Streptococcus mutans incubated at pH 4.5 and 6.5 was studied using lactic acid production from 0.1% sucrose as an indicator of fermentation activity. Cells incubated with FAP produced significantly less lactic acid than did cells incubated with hydroxyapatite (HAP). Addition of HAP to cell suspensions containing FAP reduced this inhibition, suggesting that dissolution of the FAP was necessary for inhibition. Incubation with low concentrations of NaF showed significant inhibition in cell suspensions incubated with as little as 0.45 micrograms/mL F at pH 5.0. These results provide further support to the hypothesis that fluoride levels in plaque and enamel, achievable through use of fluoridated water and/or fluoride dentifrices, may produce appreciable inhibition of glycolysis at the acidic pH levels which are readily achieved in plaque. Thus, bacterial acid production may activate plaque and enamel-bound fluoride, resulting in inhibition of further acid production, and thereby contribute substantially to the other cariostatic mechanisms of fluoride.

Topics: Apatites; Dental Plaque; Fluorides; Hydrogen-Ion Concentration; Lactates; Lactic Acid; Streptococcus mutans

Plaque grown on terylene gauze in the mouths of 5 volunteers was treated with a mineralizing solution intermittently for 4 days to deposit fluorhydroxyapatite. Control plaque grown simultaneously was not treated. Sixteen hours after the last treatment, plaque gauzes were incubated in 0.28 M glucose under N2 at 37 degrees C. The mean pH, reached by the 5 mineralized plaques after 30 min, (4.78) was significantly higher than the mean pH reached by control plaques (4.13), a difference that was due neither to unequal microbial mass nor to unequal acid concentrations. Acid neutralization following the dissolution of apatite was probably mainly responsible for the pH differences although a small antiglycolytic effect from leached F could not be ruled out. Mineralized plaque lost on average 24 per cent of its Ca, 25 per cent of its P and 16 per cent of its F, resulting in 0.868 mM Ca, 0.676 mM P and 0.075 mM F in the supernatant. Test plaque fluid was saturated with respect to fluorapatite and only moderately undersaturated with respect to hydroxyapatite at the end of the incubation period; this could explain the pronounced caries-protective effect of plaque fluorhydroxyapatite shown previously.

Topics: Adult; Apatites; Calcium; Carboxylic Acids; Dental Plaque; Durapatite; Female; Fluorides; Glucose; Humans; Hydrogen-Ion Concentration; Hydroxyapatites; Male; Middle Aged; Phosphates

Ureolytic bacteria were detected in the plaque flora of six subjects, and included members of the genera Actinomyces, Bifidobacterium, Staphylococcus, and Streptococcus. Proportions of these organisms did not change after subjects mouthrinsed thrice daily for four days with a plaque-mineralizing solution which contained urea and mono-fluorophosphate. The effectiveness of this rinse depends on the rapid metabolism of urea to alkali by plaque organisms, causing fluoridated apatite to precipitate in the matrix. Analysis of our data suggests that a numerically minor component of the flora, with a high turnover rate, is responsible for most of the ureolysis and the subsequent mineral precipitation.

Topics: Actinomyces; Adult; Apatites; Bacteria; Chemical Precipitation; Dental Plaque; Humans; Mouthwashes; Staphylococcus; Streptococcus; Urea