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Fluoride release and recharge in giomer, compomer and resin composite.

OBJECTIVES: The aim of this study was to examine the fluoride recharging and releasing abilities of resin-based materials containing fluoridated glass filler to determine whether the extent of the glass-ionomer matrix of the material affects these properties. METHODS: Three materials having a different proportion of the hydrogel matrix surrounding the glass filler, namely: Reactmer paste, Dyract AP and Xeno CF, were used for this study. Five disk specimens of each material were placed into distilled/deionized water and the fluoride release measured during 38 days. For fluoride recharge the disks were exposed to 250 ppm F solution for 1 h and the pre- and post-recharge fluoride release were determined using an ion-selective electrode (total fluoride ions) and ion chromatography (free fluoride ions). RESULTS: The amounts of total and free fluoride release from each material at the initial period in descending order were Reactmer paste > Dyract AP > Xeno CF (p < 0.05 ANOVA and Scheffe's test). After fluoride recharge, Reactmer paste showed a greater amount of fluoride release than the other materials. Dyract AP and Xeno CF showed a similar total level of fluoride release after recharging. For Xeno CF the amount of total fluoride released after recharging was significantly greater than that of free fluoride, but there was no significant difference between total and free fluoride released after recharging for Dyract AP (p = 0.05 paired t-test). SIGNIFICANCE: These results suggested that the extent of the glass-ionomer matrix of the glass filler played an important role for fluoride-releasing and recharging abilities of the resin-based materials.

Analysis of Variance↗

Formulation and characterization of a novel fluoride-releasing dental composite.

OBJECTIVES: The aims of this study were to formulate a novel fluoride-releasing dental composite and to evaluate its mechanical properties, fluoride release and recharge capabilities, water sorption and solubility. METHODS: A fluoride-releasing dimethacrylate monomer containing a ternary zirconium fluoride chelate was synthesized. Three experimental fluoride-releasing composites were fabricated with different monomer formulas (wt.%)-(1) Control A: 40 BisGMA/40 TEDMA/20 UEDMA; (2) EXPERIMENTAL: 20 F-releasing monomer/20 BisGMA/40 TEDMA/20 UEDMA; (3) Control B: the same formula as Control A except that it contained 10 wt.% (of total monomer) tetrabutylammonium fluoride (TBAF), which had a fluoride content equivalent to EXPERIMENTAL. All three materials had the same filler content: 55 wt.% silanized fluoroaluminosilicate particles (0.8 microm) and 10 wt.% silanized fumed silica (14 nm). All materials contained 0.17 wt.% camphorquinone (CQ) as a photoinitiator and 0.69 wt.% ethyl-4-dimethylaminobenzoate (4EDMAB) as an accelerator. The materials were tested for fluoride release (for 184 days), fluoride recharge, compressive and flexure strength, water sorption and solubility. The data were analyzed using ANOVA and Tukey-HSD tests, and Kruskal-Wallis test. RESULTS: The experimental composite had significantly higher fluoride release and fluoride recharge capabilities than both Control composites. It had significantly better physical and mechanical properties than Control B. SIGNIFICANCE: The combined use of the fluoride-releasing dimethacrylate monomer and fluoride-releasing filler can provide sustained high fluoride release and recharge as well as acceptable mechanical and physical properties. Simply adding organic fluoride salt in the monomer yields composites with poor mechanical and physical properties.

4-Aminobenzoic Acid↗

Long-term fluoride release of some orthodontic bonding resins: a laboratory study.

OBJECTIVES: The present study compared the amounts and profiles of long term fluoride release from four commercial direct bonding resins (Light-Bond, Reliance Orthodontic Products; Rely.a. Bond, Reliance Orthodontic Products; Orthon, Orthon Dental Inc.; Fluor Ever, Macro-Chem Corporation) and one glass ionomer cement (Ketac-Cem, Espe). METHODS: The specimens were equilibrated in double-deionized water at 37 degrees C. At predetermined intervals, and up to 560 days, the fluoride concentration of the equilibrated solution was determined with a fluoride ion selective electrode. For Light-Bond and Rely.a. Bond two batches were studied and the amount of fluoride released in a 0.1 mol/L NaCl solution was also determined. Differences in the fluoride release profiles due to batch, type of solution and time were determined with a three-factor mixed design ANOVA with repeated measures on one factor. RESULTS: The fluoride release profiles of the orthodontic adhesives studied differ markedly. Initially, Fluor Ever and Ketac-Cem release comparable amounts of fluoride which are greater than those released by Orthon. After a few weeks the amounts of fluoride released by Ketac-Cem and Orthon become comparable, but are considerably higher than those released by Fluor Ever. During the first days of the elution, the amount of fluoride released by Light-Bond equals that of Orthon, but then decreases below the determination limit of the analytical method within half a year. No difference was found between the fluoride release profiles in water and the NaCl solution. However, the fluoride release profiles apparently depend on the batch. For Rely.a. Bond, the amount of fluoride released is smaller than the detection limit for the fluoride analysis. SIGNIFICANCE: The fluoride release of the orthodontic adhesives investigated markedly depends on the mechanisms responsible for the fluoride release process.

Acrylic Resins↗

Fluoride inhibition of Klebsiella aerogenes urease: mechanistic implications of a pseudo-uncompetitive, slow-binding inhibitor.

Klebsiella aerogenes urease uses a dinuclear nickel active site to catalyze the hydrolysis of urea. Here, we describe the steady-state and pre-steady-state kinetics of urease inhibition by fluoride. Urease is slowly inhibited by fluoride in both the presence and absence of substrate. Steady-state rate studies yield parallel double-reciprocal plots; however, we show that fluoride interaction with urease is not compatible with classical uncompetitive inhibition. Rather, we propose that fluoride binds to an enzyme state (E) that is in equilibrium with resting enzyme (E) and produced during catalysis. Fluoride binding rates are directly proportional to inhibitor concentration. Substrate reduces both the rate of fluoride binding to urease and the rate of fluoride dissociation from the complex, consistent with urea binding to E and E.F in addition to E. Fluoride inhibition is pH-dependent due to a protonation event linked to fluoride dissociation. Fluoride binding is pH-independent, suggesting that fluoride anion, not HF, is the actual inhibitor. We assess the kinetic results in terms of the known protein crystal structure and evaluate possible molecular interpretations for the structure of the E state, the site of fluoride binding, and the factors associated with fluoride release. Finally, we note that the apparent uncompetitive inhibition by fluoride as reported for several other metalloenzymes may need to be reinterpreted in terms of fluoride interaction with the corresponding E states.

Bacterial Proteins↗

Prevention by means of fluoride of enamel erosion as caused by soft drinks and orange juice.

Fluoride has been suggested to prevent erosion of the teeth, either after a topical treatment of the teeth or by addition of fluoride to the acidic drink. The main aim of the present study was to describe the dissolution of calcium fluoride in some soft drinks and orange juice and compare it with the amounts of calcium fluoride left on the enamel surfaces after a topical treatment. A further aim was to describe the dissolution of enamel in soft drinks and juice saturated for 3 days with solid calcium fluoride. Solid calcium fluoride was suspended in each of 10 soft drinks and orange juices and gently agitated for 72 h, after which the drinks were analyzed for calcium, phosphate and fluoride and pH was determined. To examine the erosion-preventive effect of the calcium fluoride-rich drink, intact teeth were exposed to the drinks with or without calcium fluoride. It was found that from 6 to 45 mg of calcium fluoride was dissolved per liter of drink. The more acidic the drink, the more calcium fluoride was dissolved, presumably due to HF formation. The teeth exposed to the soft drinks all showed erosion-like lesions. Very little effect of the 4-6 ppm ionic fluoride dissolved in the soft drinks was observed. In orange juice, however, the dissolved calcium fluoride established a saturation with respect to fluorapatite and consequently, the erosion-like lesion was replaced by a caries-like lesion. In conclusion, the acidic soft drinks are capable of dissolving considerable amounts of calcium fluoride and the erosion-preventive effect of even high fluoride concentrations is limited.

Analysis of Variance↗

Fluoride availability and stability of Japanese dentifrices.

The decline of dental caries in the industrialized countries can be attributed to widespread use of fluorides. The Japanese market share of dentifrices containing fluorides has increased from 12% in 1985 to 77% in 2000. For a fluoride dentifrice to be effective in the control of dental caries, an adequate concentration of the fluoride must be soluble. Several Japanese fluoride dentifrices have in their formulations calcium phosphate as an abrasive, which may react with fluoride. This study was designed to evaluate the availability and stability of fluoride in the most consumed dentifrices in Japan. The analyses were made when the dentifrices were purchased (fresh samples) and after one year of storage (aged samples) at room temperature (21.8 +/- 3.6 degrees C). Total fluoride and soluble fluoride was determined using an ion specific electrode. All dentifrices showed similar concentrations of total fluoride in fresh and aged samples in accordance with the Japanese Legislation (content of less than 1,000 ppm F). Some dentifrices, with dicalcium phosphate as abrasive, showed decreasing concentrations of total soluble fluoride and increasing amounts of insoluble fluoride over time. Although most of the Japanese fluoridated dentifrices evaluated in this study contain unstable fluoride, they were found to have sufficient concentrations of soluble fluoride to be effective in preventing dental caries.

Biological Availability↗

[Evaluation and analysis on the micro-determination of fluoride in serum and finger blood].

The relationship of fluoride concentration between blood serum from vein and blood from finger tip was explored. Ninety people exposed to different levels of fluoride were selected. Group A was exposed directly to high level of fluoride, group B was exposed indirectly to median level of fluoride, group C was exposed to low level of fluoride and group D had no fluoride exposure. The fluoride concentration was determined by using a modified micro-fluoride electrode. The concentration of fluoride changed obviously with the delay of reservation. The fluoride concentrations of finger blood tested within one day from the four groups were different (A > B > C > D). The fluoride concentration in serum was lower compared with that in finger blood. The results showed that serum fluoride was correlated with finger blood fluoride within one day of reservation (r = 0.87). The regression equation was Y = 0.62X + 0.023. It was concluded that the determination of fluoride from finger blood could substitute for serum to reflect the level and degree of fluoride burden of body.

Adult↗

[The dose-effect relationship of water fluoride levels and renal damage in children].

OBJECTIVE: To explore the dose-effect relationship of water fluoride levels and renal damage in children and observe the difference of renal function between high-loaded fluoride people and dental fluorosis people in the same water fluoride level region. METHODS: 210 children were divided into seven groups in term of drinking water fluoride levels and whether they suffered from dental fluorosis. Fluoride concentrations in urine and serum and activities of urine NAG and gamma-GT were determined. RESULTS: The urine and serum fluoride of high-loaded fluoride people and dental fluorosis people increased compared with control, moreover fluoride contents in urine and serum increased gradually with the increase of fluoride level in drinking water. Urine NAG and gamma-GT activities significantly increased in dental fluorosis people from area of 2.58 mg/L fluoride in drinking water and in those two groups from area of 4.51 mg/L fluoride in drinking water. Moreover, there existed an obvious dose-effect relationship between the drinking water fluoride concentration and NAG and gamma-GT activity. CONCLUSION: Over 2.0 mg/L fluoride in drinking water can cause renal damage in children, and the damage degree increases with the drinking water fluoride content. Renal damage degree is not related to whether the children suffered from dental fluorosis and mainly due to water fluoride concentration.

Adolescent↗

Fluoride balance and tissue concentrations: effect of dose frequency.

The possible effects of dose frequency on the bioavailability, balance and tissue levels of fluoride were determined using young adult rats. It was hypothesized that, because of the rapidly exchangeable pool of fluoride in calcified tissues, smaller and more frequent doses of fluoride would increase the retention of fluoride in the body. All groups were fed a low-fluoride, semi-purified diet throughout the six-week study. Group B received water with 25 ppm fluoride ad libitum. Groups C, D, and E received fluoride in amounts similar to that of group B but by ig intubation one or three times each day or by ip injection once each day. Group A received fluoride only in the food. Two 24-h fluoride intake and excretion determinations were made during each week. Plasma, enamel and femur epiphysis fluoride levels were determined at the end of the study. Compared with group B, the average fluoride absorption and balance values were 13% and 10% higher, respectively, in groups C, D and E. Plasma and calcified tissue fluoride levels were also slightly higher in the latter groups but, in general, the differences were not statistically significant. In the ip-injected group, the fecal excretion of fluoride was 96% greater than the amount ingested with the diet which indicated net intestinal secretion. It was concluded that, for a given level of intake, dose frequency has only minor effects on the absorption, balance and tissue levels of fluoride in the rat. The influence of the rapidly exchangeable calcified tissue fluoride pool on the general metabolism of the ion appears to be limited when intake occurs at least once each day.

Absorption↗

Fluoride metabolism and renal osteodystrophy in regular dialysis treatment.

Fluoride in plasma, urine and bone tissue ash were estimated using a fluoride-ion electrode in 20 control persons (CP), 32 patients with compensated chronic renal failure (CRFP) and 59 patients in RDT (RDTP). The increase in plasma fluoride (CP: 2.4 +/- 1.4, CRFP: 6.5 +/- 2.2, RDTP: 12.3 +/- 4.5 mumol/L) and bone fluoride (CP: 55.1 +/- 31, CRFP: 99.9 +/- 31.2, RDTP: 339.1 +/- 150.6 mumol/g) significantly correlated with the decrease of residual glomerular filtration rate (RGFR), in RDT with the number of haemodialysis, so that the maximum increase in fluoride was found in completely anuric patients (379.7 +/- 153 mumol/g). The increase in fluoride retention was intensified by body retention of considerable amounts of fluoride each dialysis (the fluoridated dialysate increased the post-dialysis plasma fluoride by 195%). Development of bone fluorose known to develop with a bone fluoride greater than 180 mumol/g was not found in any of 40 iliac crest trephine bone biopsy specimens. No correlation was found between laboratory and histological findings of renal osteodystrophy and plasma or bone fluoride. No patient developed spontaneous fractures even after 11 years of using fluoridated dialysate. In conclusion, this report indicates that fluoride might have a protective effect against the progression of renal osteodystrophy in patients with high retention values. The longer the exposure of RDT patients to the fluoridated dialysate, the greater the bone fluoride concentration.

Adult↗

[Interaction of fluoride with milk constituents].

Fluoride concentrations have been studied in cow milk stemming from regions variably influenced by fluorine pollution. It was disclosed that fluoride concentration in the milk of cows grazing on areas with a high degree of environmental contamination by fluorine compounds was about three-fold higher as compared to the control group. Fluoride distribution was evaluated in milk, in which the protein sediment got separated from the whey. The said distribution was found to be equal in both of the milk constituents. Due to the decomposition of whey into the whey proteins sediment and the remaining solution, an answer was obtained to the question of which part of whey fluoride appeared in the ionized form (80%). Studying the binding of fluoride by isolating and purifying the fraction of milk proteins at various pH, it was revealed that alpha-lactalbumin bound fluoride at 3.9 pH. Because of limited caseins solubility at that pH, there was no possibility to find out whether they bound fluoride ions. At fresh milk pH, the caseins exist in the anionic form and as such they are unable to bind fluoride independently. The binding of fluoride with milk lipids was investigated and it was ascertained that about 11% of fluoride being introduced into milk were bound to lipid constituent. The study covered also the influence of fluoride ions on the magnitude of the optic polarization angle of aqueous lactose solutions in different concentrations. That angle undergoes diminution in comparison with solutions not polluted by fluoride. Fluoride concentration was defined in some milk formulas of Polish production designed for infants. They exceed, depending on the kind of formulas, 20-70 fold the average fluoride concentration evidenced in human milk. Thus, the differences in fluoride supplied to infants, fed by breast and artificially, are very great.

Animals↗

Rational use of fluorides in caries prevention. A concept based on possible cariostatic mechanisms.

The aim of this review has been to suggest that future fluoride preventive programs should be based on what is at present known about the possible cariostatic mechanisms of fluoride. The relative role of enamel fluoride in caries prevention has become increasingly questioned during the last two decades. No significant relationship has been demonstrated between caries experience of the individual and fluoride content of the enamel. Furthermore, the fluoride content in surface enamel between teeth developed in low and "optimal" fluoride areas is too small to explain any significant effect on dissolution rate of the enamel. As the major explanation for the cariostatic effect of fluoride must therefore be sought in its local effect on the oral environment, the possible effects on plaque colonization, composition and metabolic activities are discussed. The effect of even low concentrations of fluoride in the liquid phase on enamel dissolution is described, and it is concluded that the major cariostatic effect of water fluoridation, fluoride tooth paste and mouth rinses can probably be ascribed to regular increases in fluoride ion activity in the oral fluids. The effect of high concentrations of topical fluoride solutions is thought to be a result of a slow dissolution of calcium fluoride deposited in initial caries lesions, whereby an increased fluoride ion concentration is maintained locally for longer periods of time. Finally, the clinical consequences of these considerations are described.

Adolescent↗

Dietary fluoride supplements for Nebraska's children--the role of the physician.

1. All children should receive one form of systemic fluoride and appropriate forms of topical fluoride. 2. If a child is not receiving optimally fluoridated water, the physician or dentist should prescribe dietary fluoride supplements (tablets or drops). 3. The correct dosage must be determined based on patient age and fluoride content of the patient's main water source(s). 4. Special attention is necessary concerning fluoride intake for children breast-feeding or consuming infant formula. 5. To arrive at the correct fluoride dose, these steps should be followed: A. Always have a sample of the main drinking water source (usually home water) analyzed for the fluoride content before prescribing a fluoride supplement, if you do not have other specific knowledge of water fluoride content. The Laboratory Division of the Nebraska State Department of Health provides water fluoride assay services. B. When the fluoride content of the water has been determined, the fluoride level and the child's age should be matched on Table 1 to arrive at the correct supplement dose. 6. The Division of Dental Health of the Nebraska State Department of Health can provide lists of communities and schools in Nebraska that are optimally fluoridated.

Adolescent↗

CaF2 in enamel biopsies 6 weeks and 18 months after fluoride treatment.

Fluoride concentrations were studied in enamel biopsies from maxillary central incisors 6 weeks and 18 months after fluoride treatment. In the short-term study biopsies were obtained prior to and after treatment with acidic sodium or ammonium fluoride. The findings showed that large amounts of fluoride were deposited in enamel from NH4F treatment (mean concentration 84,723 ppm), indicating substantial CaF2 formation. NaF treatment resulted in mean fluoride concentrations of 7,818 ppm. In the 18-month study, biopsies from 58 placebo-treated teeth were analyzed for total fluoride (mean 1,733 ppm). Twenty-five additional biopsies from placebo-treated and 58 from NH4F-treated teeth were analyzed for KOH-soluble (CaF2) and KOH-nonsoluble (apatitic) fluoride. The mean values for total fluoride were 1,669 and 2,085 ppm in the placebo-treated and in the NH4F-treated groups, respectively. The corresponding mean values for KOH-nonsoluble fluoride were 1,467 and 1,731 ppm and for KOH-soluble fluoride 202 and 354 ppm, respectively. The increase in enamel fluoride after fluoride treatment was only marginally significant. Biopsies from the ammonium fluoride treated group were significantly more likely to have high (30 vs. 8%) and moderate (28 vs. 16%) CaF2 levels and less likely to have low levels than biopsies of placebo-treated teeth (chi-square = 8.0 with 2 d.f.; p = 0.018). It is concluded that very substantial amounts of CaF2 are present in enamel 6 weeks after treatment, and small amounts may persist in the surface enamel for as long as 18 months.

Adolescent↗

Fluoride in UK rivers.

Fluoride concentrations in eastern UK rivers (the Humber, Tweed, Wear, Great Ouse and Thames) are described based on information collected within the Land-Ocean Interaction Study (LOIS) and by the Environment Agency (EA) of England and Wales. The results show varied fluoride concentrations across the region, with a range from <0.01 to >10 mg l(-1); and mean, median and range in mean concentrations of 0.30, 0.21 and 0.05-3.38 mg l(-1) (excluding one outlier point), respectively. Within the main rivers and tributaries, the mean fluoride concentration varied from approximately 0.5 to over 2 mg l(-1) and the highest values occurred within the Don basin (Don, Dearne and Rother) and parts of the Trent basin (upper Tame and mid-upper Derbyshire Derwent) in highly industrialised and urbanised areas (Sheffield and Rotherham in the Don basin; Birmingham and Derby on the Trent). For localised inputs to the rivers, fluoride concentrations were slightly higher, and considerably higher in one outlier case. Correspondingly, the other rivers examined typically had mean fluoride concentrations between approximately 0.2 and 0.5 mg l(-1), but fluoride concentrations were lower in the headwater areas. As there is much less information on fluoride levels in upland areas, extensive data collected as part of an acid waters survey are used to show that fluoride concentrations are generally less than 0.1 mg l(-1) for the upland UK. The data are summarised in terms of both fluoride concentrations and flux, and the values are cross-referenced to other determinands collected within LOIS. The high positive correlation with boron and negative correlation with flow show the importance of point source (sewage) inputs of fluoride, while strong positive correlations between fluoride and barium indicate the relative importance of vein mineralisation in the bedrock in supplying fluoride to the waters of the Yorkshire Ouse and its tributaries. There seems to be some process that limits the fluoride concentrations within the more contaminated rivers, and this is indicated by a negative upper bound between fluoride and calcium. The waters are undersaturated with respect to fluorite and oversaturated with respect to calcium fluoro-phosphates. This upper bound may reflect either physical controls, such as the availability and size of point and diffuse sources for fluoride coupled to mixing of these sources with rain and soil runoff of low concentration, or solubility controls for a pure or mixed-phase mineral that cannot be specified here.

Journal Article↗

The effective use of fluorides in public health.

Dental caries remain a public health problem for many developing countries and for underprivileged populations in developed countries. This paper outlines the historical development of public health approaches to the use of fluoride and comments on their effectiveness. Early research and development was concerned with waterborne fluorides, both naturally occurring and added, and their effects on the prevalence and incidence of dental caries and dental fluorosis. In the latter half of the 20th century, the focus of research was on fluoride toothpastes and mouth rinses. More recently, systematic reviews summarizing these extensive databases have indicated that water fluoridation and fluoride toothpastes both substantially reduce the prevalence and incidence of dental caries. We present four case studies that illustrate the use of fluoride in modern public health practice, focusing on: recent water fluoridation schemes in California, USA; salt fluoridation in Jamaica; milk fluoridation in Chile; and the development of "affordable" fluoride toothpastes in Indonesia. Common themes are the concern to reduce demands for compliance with fluoride regimes that rely upon action by individuals and their families, and the issue of cost. We recommend that a community should use no more than one systemic fluoride (i.e. water or salt or milk fluoridation) combined with the use of fluoride toothpastes, and that the prevalence of dental fluorosis should be monitored in order to detect increases in or higher-than-acceptable levels.

Adolescent↗

Influence of carbamide peroxide on enamel fluoride uptake.

OBJECTIVE: Aim of the study was to evaluate the influence of carbamide peroxide (CP) on enamel fluoride uptake by comparing enamel fluoride uptake from a 1% amine fluoride (AmF) gel with the fluoride acquisition from a 10% carbamide peroxide agent supplemented with 1% AmF. MATERIALS AND METHODS: Three enamel cylinders (4mm in diameter) were prepared from the buccal surfaces of 60 bovine incisors. One sample of each tooth was used for determination of baseline fluoride content of the respective tooth. The two remaining samples were allocated to the experimental series 1 or 2, respectively. Each series consisted of five experimental groups (A-E, n=12) and differed with respect to the length of the treatment period with the gels (A-D). The experimentally designed gels (pH 5.5) used in the study were as follows: A (10% CP), B (10% CP, 1% F(-) as AmF), C (1% F(-) as AmF), D (no CP, no F(-)) and were formulated on the same basis. The enamel samples were covered for 4h with the respective gel at 37 degrees C and were then transferred to artificial saliva for 20 h (series 1). The samples of group E served as controls and were not treated with a gel. In series 2, treatment with the gels and storage in saliva was conducted seven times. Finally, the samples were assessed for KOH-soluble and structurally bound fluoride. RESULTS: Only the enamel samples treated with the fluoridated bleaching gel (group B) and with the amine fluoride gel (group C) exhibited significant fluoride acquisition. Thereby, both gels showed significantly lower uptake in series 1 as compared to series 2. Both KOH-soluble and structurally bound fluoride acquisition was significantly higher in group C than in group B. CONCLUSION: Treatment with a carbamide peroxide gel supplemented with amine fluoride causes less fluoride acquisition in enamel than a pure amine fluoride gel. Under the conditions of the study, it is assumed that carbamide peroxide seems to influence enamel fluoride uptake.

Amines↗

Current concepts on the theories of the mechanism of action of fluoride.

The caries-preventive effect of fluoride is mainly attributed to the effects on demineralization/remineralization at the tooth oral fluids interface. Sub ppm levels of fluoride in saliva are effective in shifting the balance from demineralization, leading to caries, to remineralization. This is attributed to the fluoride-enhanced precipitation of calcium phosphates, and the formation of fluorhydroxyapatite in the dental tissues. Low fluoride levels are found in saliva after toothbrushing with fluoride containing dentifrices. Similar concentrations are ineffective in interfering with processes of growth and metabolism of bacteria, and also do not result in a significantly reduced dissolution of tooth mineral as a result of (firmly bound) fluoride incorporation. Comparative studies of fluoride efficacy have shown that higher concentrations in solution are needed in pH-cycling studies of dentine than in enamel to maintain the mineral balance or to induce remineralization. This is attributed to the greater solubility of the dentine and the smaller size of the dentine crystallites compared to enamel. Fluoride slow-release devices, in the form of fluoride-releasing restorative materials, may serve to increase the fluoride levels in saliva and plaque to levels at which caries can be prevented, also in high-risk patients. Research questions for the next millennium and future perspectives for fluoride applications should be found in the retention and slow release of fluoride after various combinations of fluoride treatment, the combination of fluoride and anti-microbial treatment, the individualization of caries prevention, and the combination of preventive schemes with new developments in caries diagnosis.

Cariostatic Agents↗