Dentine caries inhibition through CO(2) laser (10.6 mu m) irradiation and fluoride application, in vitro

Objective: The purpose of the study was to investigate whether dentine irradiation with a pulsed CO(2) laser (10.6 mu m) emitting pulses of 10 ms is capable of reducing dentine calcium and phosphorus losses in an artificial caries model. Design: The 90 dentine slabs obtained from bovine teeth were randomly divided into six groups (n = 15): negative control group (GC); positive control group, treated with fluoride 1.23% (GF); and laser groups irradiated with 8 J/cm(2) (L8); irradiated as in L8 + fluoride 1.23% (L8F); irradiated with 11j/cm(2) (L11); irradiated as in L11 + fluoride 1.23% (L11F). After laser irradiation the samples were submitted to a pH-cycling model for 9 days. The calcium and phosphorous contents in the de- and remineralization solutions were measured by means of inductively coupled plasma optical emission spectrometer - ICP-OES. Additionally intra-pulpal temperature measurements were performed. The obtained data were analysed by means of ANOVA and Tukey`s test (alpha = 0.05). Results: In the demineralization solutions the groups L11F and GF presented significantly lower means of calcium and phosphorous losses than the control group; and in L11F means were significantly lower than in the fluoride group. Both irradiation parameters tested caused intrapulpal temperature increase below 2 degrees C. Conclusion: It can be concluded that under the conditions of this study, CO(2) laser irradiation (10.6 mu m) with 11J/cm(2) (540 mJ and 10 Hz) of fluoride treated dentine surfaces decreases the loss of calcium and phosphorous in the demineralization process and does not cause excessive temperature increase inside the pulp chamber. (C) 2010 Elsevier Ltd. All rights reserved.

Fluoride uptake and acid resistance of enamel irradiated with Er : YAG laser

This study evaluated the resistance to demineralization and fluoride incorporation of enamel irradiated with Er:YAG. A total of 110 bovine teeth were selected and divided into eight groups: unlased, 37% phosphoric acid, and samples irradiated with the Er:YAG laser at several fluences (31.84 J/cm(2), 25.47 J/cm(2), 19.10 J/cm(2), 2.08 J/cm(2), 1.8 J/cm(2), and 0.9 J/cm(2)). The application of acidulated phosphate fluoride was performed after treatments. All samples were immersed in 2 ml of 2.0 M acetic-acetate acid solution at pH 4.5 for 8 h, and fluoride, calcium, and phosphorus ions dissolved were analyzed by atomic absorption spectrometry and spectrophotometry. The phosphoric acid and 31.84 J/cm(2) groups presented the lowest dissolution of calcium and phosphorus ions. Higher fluoride incorporation was observed on 1.8 J/cm(2) and 0.9 J/cm(2) groups. Based on these results, Er:YAG laser was able to decrease acid dissolution and increase fluoride uptake and can be a promissory alternative for preventive dentistry.

The Effect of Fluoride Therapies on the Morphology of Bleached Human Dental Enamel

The aim of this in vitro study was to evaluate qualitatively the surface morphology of enamel bleached with 35% hydrogen peroxide (HP) followed by application of fluoridated agents. Forty intact pre molars were randomly distributed into four groups (n = 10), treated as follows: Group I (control group) remained stored in artificial saliva at 37 degrees C, Group II - 35% HP; Group III - 35% HP + acidulated fluoride (1.23%) and Group IV - 35% HP + neutral fluoride (2%). The experimental groups received three applications of bleaching gel and after the last application all specimens were polished. This procedure was repeated after 7 and 14 days, and during the intervals of applications, the specimens were stored in artificial saliva at 37 degrees C. Scanning electron microscopy (SEM) analysis showed superficial irregularities and porosities to varying degrees in bleached enamel compared to control group. Sample evaluation was made by attributing scores, and data were statistically analyzed using Kruskal-Wallis and Dunn tests (P < 0.05). SEM qualitative investigation demonstrated that 35% hydrogen peroxide affected human dental enamel morphology, producing porosities, depressions, and superficial irregularities at various degrees. These morphological changes were higher after the application of 1.23% acidulated fluoride gel. Microsc. Res. Tech. 74:512-516, 2011. (C) 2010 Wiley-Liss, Inc.

Proteomic Analysis of Urine in Rats Chronically Exposed to Fluoride

Urine is an ideal source of materials to search for potential disease-related biomarkers as it is produced by the affected tissues and can be easily obtained by noninvasive methods. 2-DE-based proteomic approach was used to better understand the molecular mechanisms of injury induced by fluoride (F(-)) and define potential biomarkers of dental fluorosis. Three groups of weanling male Wistar rats were treated with drinking water containing 0 (control), 5, or 50 ppm F(-) for 60 days (n = 15/group). During the experimental period, the animals were kept individually in metabolic cages, to analyze the water and food consumption, as well as fecal and urinary F excretion. Urinary proteome profiles were examined using 2-DE and Colloidal Coomassie Brilliant Blue staining. A dose-response regarding F(-) intake and excretion was detected. Quantitative intensity analysis revealed 8, 11, and 8 significantly altered proteins between control vs. 5 ppm F(-), control vs. 50 ppm F(-) and 5 ppm F(-) vs. 50 ppm F(-) groups, respectively. Two proteins regulated by androgens (androgen-regulated 20-KDa protein and 0c-2,1-globulin) and one related to detoxification (aflatoxin-Bl-aldehyde-reductase) were identified by MALDI-TOF-TOF MS/MS. Thus, proteomic analysis can help to better understand the mechanisms underlying F(-) toxicity, even in low doses. 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:8-14, 2011; View this article online at wileyonlinelibrary.com. DOI 10:1002/jbt.20353

Effect of Different Fluoride Concentrations of Experimental Dentifrices on Enamel Erosion and Abrasion

It has been suggested that fluoride products are able to reduce erosive tooth wear. Thus, the purpose of this in vitro study was to evaluate the effect of dentifrices with different fluoride concentrations as well as of a low-fluoridated dentifrice supplemented with trimetaphosphate (TMP) on enamel erosion and abrasion. One hundred twenty bovine enamel blocks were assigned to the following experimental dentifrices: placebo, 1,100 mu g F/g, 500 mu g F/g plus 3% TMP and 5,000 mu g F/g. The groups of enamel blocks were additionally subdivided into conditions of erosion (ERO) and of erosion plus abrasion (ERO + ABR). For 7 days, the blocks were subjected to erosive challenges (immersion in Sprite (R) 4 times a day for 5 min each time) followed by a remineralizing period (immersion in artificial saliva between erosive challenges for 2 h). After each erosive challenge, the blocks were exposed to slurries of the dentifrices (10 ml/sample for 15 s). Sixty of the blocks were additionally abraded by brushing using an electric toothbrush (15 s). The alterations of the enamel were quantified using the Knoop hardness test and profilometry (measurements in micrometers). The data were analyzed using a 2-way ANOVA test followed by a Bonferroni correction (p < 0.05). In in vitro conditions, the 5,000 mu g F/g and 500 mu g F/g plus 3% TMP dentifrices had a greater protective effect when compared with the 1,100 mu g F/g dentifrice, under both ERO and ERO + ABR conditions. The results suggest that dentifrices alone are not capable of completely inhibiting tooth wear. Copyright (C) 2010 S. Karger AG, Basel

Influence of Genetic Background on Fluoride Metabolism in Mice

A/J and 129P3/J mouse strains have different susceptibilities to dental fluorosis, due to their genetic backgrounds. This study tested whether these differences are due to variations in water intake and/or F metabolism. A/J (susceptible to dental fluorosis) and 129P3/J mice (resistant) received drinking water containing 0, 10, or 50 ppm F. Weekly F intake, excretion and retention, and terminal plasma and femur F levels were determined. Dental fluorosis was evaluated clinically and by quantitative fluorescence (QF). Data were tested by two-way ANOVA. Although F intakes by the strains were similar, excretion by A/J mice was significantly higher due to greater urinary F excretion, which resulted in lower plasma and femur F levels. Compared with 129P3/J mice given 50 ppm F, significantly higher QF scores were recorded for A/J mice. In conclusion, these strains differ with respect to several features of F metabolism, and amelogenesis in the 129P3/J strain seems to be unaffected by high F exposure.

Effect of sodium, amine and stannous fluoride at the same concentration and different pH on in vitro erosion

Objective: This study aimed to compare the effects 0.5% and 1% sodium, amine and stannous fluoride at different pH on enamel erosion in vitro. Methods: Bovine enamel samples were submitted to a cyclic de- and remineralisation for 3 days. Each day, the samples were exposed for 120 min to pooled human saliva and subsequently treated with one of the fluoride solutions for 3 min: amine fluoride (AmF, 0.5% and 1% F(-)), sodium fluoride (NaF, 0.5% and 1% F(-)), each at pH 3.9 and 7.0, and stannous fluoride (SnF(2), 0.5% and 1% F-), at pH: 3.9. Additionally, two groups were treated with fluoride-free placebo solutions (pH: 3.9 and 7.0) and one group served as control (no fluoridation). Ten specimens each group were inserted in a so-called artificial mouth and eroded six times daily with hydrochloric acid (pH 2.6) for 90 s each intermitted by exposure to artificial saliva (1 h). After 3 days, enamel loss was analyzed profilometrically and evaluated statistically by ANOVA. Results: Only the acidic 0.5% and 1% SnF(2) and 1% AmF solutions were able to reduce erosive enamel loss significantly, while all other solutions and placebos did not differ significantly from the control. Between the acidic SnF(2) and the 1% AmF solutions no significant differences could be detected. Conclusion: At the same concentrations, acidic SnF(2) and AmF may be more effective than NaF to protect enamel against erosion. (C) 2009 Elsevier Ltd. All rights reserved.

Proteomic analysis of kidney in rats chronically exposed to fluoride

Two-dimensional gel electrophoresis (2-DE) was used to better understand alterations in renal metabolism induced by fluoride (F). Three groups of weanling male Wistar rats were treated with drinking water containing 0 (control), 5, or 50 ppm F for 60 days (n=6/group). Kidneys were collected for proteomic and histological (HE) analysis. After protein isolation, renal proteome profiles were examined using 2-DE and Colloidal Coomassie Blue staining. Protein spots with a 2-fold significant difference as detected by quantitative intensity analysis (image Master Platinum software) and t-test (p < 0.05) were excised and analyzed by MALDI-TOF MS (matrix assisted laser desorption ionization-time-of-flight mass spectrometry). The histological analysis revealed no damage in kidneys induced by F, except for a vascular congestion in the 50 ppm F group. Between control vs 50 ppm F, and control vs 5 ppm F groups, 12 and 6 differentially expressed proteins were detected, respectively. Six proteins, mainly related with metabolism, detoxification and housekeeping, were successfully identified. At the high F group, pyruvate carboxylase, a protein involved in the formation of oxaloacetate was found to be downregulated, while enoyl coenzyme A hydratase, involved in fatty acids oxidation, was found to be upregulated. Thus, proteomic analysis can provide new insights into the alterations in renal metabolism after F exposure, even in low doses. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Dietary Fluoride Intake by Children Receiving Different Sources of Systemic Fluoride

There has been no comparison of fluoride (F) intake by pre-school children receiving more traditional sources of systemic F. The aim of this study was to estimate the dietary F intake by children receiving F from artificially fluoridated water (AFW-Brazil, 0.6-0.8 mg F/L), naturally fluoridated water (NFW-Brazil, 0.6-0.9 mg F/L), fluoridated salt (FS-Peru, 180-200 mg F/Kg), and fluoridated milk (FM-Peru, 0.25 mg F). Children (n = 21-26) aged 4-6 yrs old participated in each community. A non-fluoridated community (NoF) was evaluated as the control population. Dietary F intake was monitored by the ""duplicate plate"" method, with different constituents (water, other beverages, and solids). F was analyzed with an ion-selective electrode. Data were tested by Kruskall-Wallis and Dunn`s tests (p < 0.05). Mean (+/- SD) F intake (mg/Kg b.w./day) was 0.04 +/- 0.01(b), 0.06 +/- 0.02(a,b), 0.05 +/- 0.02(a,b), 0.06 +/- 0.01(a), and 0.01 +/- 0.00(c) for AFW/NFW/FS/FM/NoF, respectively. The main dietary contributors for AFW/NFW and FS/FM/NoF were water and solids, respectively. The results indicate that the dietary F intake must be considered before a systemic method of fluoridation is implemented.

The Effect of Different Fluoride Concentrations and pH of Dentifrices on Plaque and Nail Fluoride Levels in Young Children

To evaluate the influence of dentifrice pH and fluoride (F) concentration on F uptake by plaque and nails, two sets of 5-to 6-year-old children were randomly allocated into four groups, according to the type of dentifrice they had been using for 1 year: (1) experimental liquid dentifrice (ELD), 1,100 ppm F, pH 7.0; (2) ELD, 1,100 ppm F, pH 4.5; (3) ELD, 550 ppm F, pH 4.5, and (4) commercial toothpaste, 1,100 ppm F, pH 7.0. In one set of children, nails were clipped. In the second, plaque samples were collected 1 h after the last use of dentifrice. F concentration in plaque and nails was analyzed. Plaque F concentration was significantly lower in group 4 than in groups 1-3. Nail F concentration was significantly higher in group 4, and significantly lower in group 3, than in group 1 or 2. Plaque F uptake was influenced significantly by dentifrice consistency and nonsignificantly by pH and F concentration. Reduction of dentifrice pH did not affect nail F concentration. Copyright (C) 2009 S. Karger AG, Basel

Environmental and Individual Factors Associated with Nail Fluoride Concentration

Nails have been suggested as suitable biomarkers of exposure to F, with the advantage of being easily obtained. The effect of water F concentration, age, gender, nail growth rate and geographical area on the F concentration in the fingernail and toenail clippings were evaluated. Volunteers (n = 300) aged 3-7, 14-20, 30-40 and 50-60 years from five Brazilian communities (A-E) participated. Drinking water and nail samples were collected and F concentration was analyzed with the electrode. A reference mark was made on each nail and growth rates were calculated. Data were analyzed by ANOVA and linear regression (alpha = 0.05). Mean water F concentrations (8 SE, mg/l) were 0.09 +/- 0.01, 0.15 +/- 0.01, 0.66 +/- 0.01, 0.72 +/- 0.02, and 1.68 +/- 0.08 for A-E, respectively. Mean F concentrations (+/- SE, mg/kg) ranged between 1.38 +/- 0.14 (A, 50-60 years) and 10.20 +/- 2.35 (D, 50-60 years) for fingernails, and between 0.92 +/- 0.08 (A, 14-20 years) and 7.35 +/- 0.80 (E, 50-60 years) for toenails. Among the tested factors, geographical area and water F concentration exerted the most influence on finger- and toenail F concentrations. Subjects of older age groups (30-40 and 50-60 years) from D and E showed higher nail F concentrations than the others. Females presented higher nail F concentration than males. Water F concentration, age, gender and geographical area influenced the F concentration of finger- and toenails, and hence should be taken into account when using this biomarker of exposure to predict risk for dental fluorosis. Copyright (C) 2009 S. Karger AG, Basel

Daily variations in human plasma fluoride concentrations

This study investigated the variations in human plasma fluoride concentrations ([F]) and sought to determine the causes. Five subjects (27-33 years old) received a low-F diet during the 5 days of the study. Plasma samples and urine were collected every 3 h from 8 a.m. to 8 p.m. F, PTH, Ca and P were analyzed with the electrode, by chemiluminescence, AAS and colorimetry, respectively. A trend for the plasma [F] was found. The peak [F], 0.55 +/- 0.11 mu mol L(-1), occurred at 11 a.m. and the lowest [F], 0.50 +/- 0.06 mu mol L(-1) occurred between 5 and 8 p.m. Plasma [F] were positively correlated with urinary F excretion rates and with serum PTH levels, but not with the Ca or P levels. Serum PTH levels were positively correlated with urinary F excretion rates and negatively correlated with plasma Ca. The results suggest that the renal system seems to control the daily fluctuations in plasma [F]. (c) 2008 Elsevier B.V. All rights reserved.

Pharmacokinetics of ingested fluoride: Lack of effect of chemical compound

Fluoride in drinking water may be present from natural sources or added as sodium fluoride (NaF), sodium silicofluoride (Na2SiF6) or fluorosilicic acid (H2SiF6). Results from an early study with rats suggested that, when ingested as Na2SiF6, the absorption and excretion of fluoride were greater than when ingested as NaF. Objective: The present single-blind, crossover study with 10 adults was done to determine three key pharmacokinetic parameters: the maximum plasma fluoride concentrations (C-max), the elapsed time to reach the maximum concentrations (T-max) and the 6-h areas under the time-plasma concentration curves (AUCs) after ingestion of 500 ml, of water containing 0.67 or 5.45 mg F/L present naturally or added as NaF or H2SiF6. Design: Blood was collected prior to and at nine time points during 6 h after ingestion of the test solutions. Plasma was analysed by electrode after HMDS-facilitated diffusion and the data were analysed for statistically significant differences using repeated measures ANOVA. Results: The C-max, T-max and AUC values after ingestion of the solutions containing natural fluoride, NaF or H2SiF6 did not differ significantly at either dose level. Further, the Tmax values associated with the 0.67 and SAS mg/L solutions did not differ significantly indicating that the absorption, distribution and elimination rates were not affected by the dose size. Conclusions: Considered together with published reports, the present findings support the conclusion that the major features of fluoride metabolism are not affected differently by the chemical compounds commonly used to fluoridate water nor are they affected by whether the fluoride is present naturally or added artificially. (C) 2008 Elsevier Ltd. All rights reserved.

Bioavailability of fluoride administered as sodium fluoride or monofluorophosphate to humans

A double-bind cross-over study was conducted on four healthy subjects, aged 19-29 years, in order to determine the relative bioavailability and other pharmacokinetics features of fluoride (F) after single oral administration in fasting conditions of 2 mg F as sodium F (NaF) or sodium monofluorophosphate (MFP). The bioavailability was evaluated on the basis of the plasma levels and of the urinary excretion of F. Blood was sampled before and during the 8 h after the administration of the test solutions. For F excretion urine was sampled 12 h before the study and over the 8 h after the administration. Data were tested for statistically significant differences by ANOVA and Tukey`s post hoc tests, and also by Student`s t-test (p < 0.05). For the two formulations, the pharmacokinetics of F in plasma was characterized by a rapid absorption and by a peak (C-max = 0.1 mu g/mL) which was reached 20 min after administration, followed by a biphasic elimination. In the 8 h following the administration the urinary excretion of F accounted for 35-41% of the administered dose, without significant differences between the two formulations. The AUCs (+/- S.D.) for NaF and MFP were 21.15 (+/- 0.58) and 19.04 (+/- 1.75) min mu g mL(-1), respectively, and were not significantly different (p = 0.079). Based on the AUC and C-max of F in plasma and on the urinary excretion of F during the 8 h following administration, the relative bioavailabilities of the two F formulations were equivalent. (c) 2008 Elsevier B.V. All rights reserved.