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PubMed2005

Effects of the molar ratio of hydroxide and fluoride to Al(III) on fluoride removal by coagulation and electrocoagulation.

The effect of the molar ratio of hydroxide and fluoride ions to Al(III) ions (gamma(OH) and gamma(F)) on coagulation and electrocoagulation (EC) was studied to solve the problem of the over addition of acid or base. The efficiency of defluoridation was approximately 100% when the sum of gamma(OH) and gamma(F) (gamma(OH+F)) was close to 3. This finding reveals that the fluoride ions and the hydroxide ions can co-precipitate with Al(III) ions and the formula of the precipitate is Al(n)F(m)(OH)(3n-m). However, when gamma(OH) was less than 2.4, the defluoridation efficiency, given that gamma(OH+F)=3, dropped as gamma(OH) fell, because the amount of aluminum polymer formed dropped. The efficiency of defluoridation of EC exceeded that of coagulation for equal gamma(OH) and gamma(OH+F), when gamma(OH+F)>3, proving the existence of an electrocondensation effect.

Journal Article↗
PubMed2005

Nucleophilic identity substitution reactions. The reaction between hydrogen fluoride and protonated alkyl fluorides.

The gas phase reactions between HF and the protonated alkyl fluorides MeFH+, EtFH+, Pr(i)FH+, and Bu(t)FH+ have been studied using ab initio methods. The potential energy profiles for both nucleophilic substitution (S(N)2) and elimination (E2) pathways have been investigated. Both backside Walden inversion and frontside nucleophilic substitution reaction profiles have been generated. Backside substitution is very favourable, but shows relatively little variation with the alkyl group. Frontside substitution reaction barriers are only slightly higher than the barrier for backside substitution for HF + MeFH+, and the difference in barrier heights for frontside and backside displacement seems negligible for the larger alkyl groups. Reaction barrier trends have been analysed and compared with the results of similar studies of the H2O/ROH2+ and NH3/RNH3+ systems (R = Me, Et, Pr(i), and Bu(t)). Compared to the two other classes, protonated fluorides have extreme structures which, with the exception of the Me substrate, are weakly bound complexes between an alkyl cation and HF. The results nourish the idea that nucleophilic substitution reactions are better understood in view of competition between frontside and backside substitution than from the traditional S(N)1/S(N)2 perspective.

Chemistry, Organic↗
PubMed1986

Toothbrush resistance and fluoride retention of sound, etched, fluoridated, and remineralized bovine enamel.

The wear resistance of tooth enamel that had undergone eight different treatments regarding the bonding procedure has been investigated. In comparison to sound enamel, the outer 3 microns of the etched-surface enamel show a decreased wear resistance against toothbrushing in vitro. Remineralization, either direct or preceded by acidified phosphated fluoride (APF) application, did not improve the wear resistance. The prophylactic effect of the APF treatment of etched enamel is considerable and is not lost after the soft, outer surface layer has worn off.

Acid Etching, Dental↗
PubMed1994

Alkali-soluble and insoluble fluoride in erupted and unerupted human enamel from a high fluoride area with a low fluorosis score.

The amounts of fluoroapatite and 'CaF2-like' fluoride (F) were determined in enamel of unerupted and erupted teeth that had been exposed in vivo to 1.8-2.6 parts/10(6) F in the drinking water and to brushing with F dentifrice at least once a day, and occasionally to a F mouth-rinse (0.022% F). Enamel was sampled by acid-etching and the F levels were measured with an adapted F ion-selective electrode. More F was built into the deeper enamel in the high-F area than in a similar low-F area. Unerupted enamel did not etch significantly (p > 0.05) deeper than erupted enamel. No significant differences (p > 0.05) were found in the F concentrations amongst the following: alkali-washed erupted, unwashed erupted, alkali-washed unerupted and unwashed unerupted at the outer most enamel (approx. 6 microns). However the erupted enamel (alkali-washed or not) showed higher F levels than unerupted enamel (alkali-washed or not) between approx. 6 microns and greater than 100 microns. The increase of F for this high-F area was about 100% in the deeper enamel while for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 microns. In contrast to a similar low-F area (water F < 0.10 parts/10(6)), no significant 'CaF2-like' F could be detected in erupted or unerupted enamel for the high-F area.

Dental Enamel↗
PubMed1989

Influence of food and antacid administration on fluoride bioavailability from enteric-coated sodium fluoride tablets.

The relative bioavailability of enteric-coated sodium fluoride (NaF) tablets (10 mg F-) has been assessed following administration with a standard calcium-rich breakfast or calcium-poor lunch, and 2 h before or simultaneously with antacid administration (2.4 g aluminum-magnesium hydroxide), versus intake on an empty stomach. Twelve volunteers were studied 3 times according to an open, three-way crossover design over a 24 h period at weekly intervals. Meals were found to decrease the peak serum concentration of NaF from 122 micrograms/L during fasting (after baseline subtraction) to 71 and 88 micrograms/L with breakfast and lunch respectively, and to slow its absorption rate with Tmax increasing from 3.3 to 7.3 and 11.2 hours, without altering its bioavailability. Antacid impaired the bioavailability of NaF by 80% when administered simultaneously, with AUC decreasing from 987 to 155 micrograms.h/L, but had no significant effect when taken 2 h before NaF. In conclusion, the enteric-coated NaF tablets used in this study can be administered with food or after a 2-hour delay following antacid administration, but should not be taken simultaneously with antacid.

Adult↗
PubMed1980

Stability of fluoride levels in surface layer of normal enamel during a 21-month fluoride mouthrinsing program.

A 21-month trial of the caries-preventive effect of a 0.2% NaF mouthrinse included monitoring changes in the concentration of F in normal enamel. Subsamples of 25 children were randomly selected from groups receiving either normal dental treatment (Control group); additional fortnightly professional prophylaxes (Test group); or prophylaxes plus fortnightly 2-min fluoride rinses (Test + F group). At the start of the trial the sound labial surface of tooth 24 (occasionally 23 or 22) was etched with 2 N HCL and the etchant analysed for F, Ca and phosphate. The contralateral tooth was sampled at the end of the trial. The caries increments (DFS) for the three groups over 21 months were Control, 2.88; Test, 2.51 and Test + F, 1.77, the last being significantly less than the others (P less than 0.05). The average sound enamel surface F concentrations were similar for the three groups at the start and the end of the trial. F parameter calculations showed that all differences were non-significant. Thus this factor could not explain the reduced caries increment due to F mouthrinsing. F biopsies for the purpose of predicting likely clinical effectiveness of neutral 0.2% NaF mouthrinsing will find little application in public health dentistry.

Adolescent↗
PubMed1989

Fluoride bioavailability from disodium monofluorophosphate fluoridated milk in children and rats.

The aim of the present work was to study the usefulness of disodium monofluorophosphate (MFP) as a milk-fluoridating agent by measuring the bioavailability of F from MFP in milk relative to that of F from NaF in water. Long-term (multiple-dose) studies were performed on rats measuring F bone uptake. The relative F absorption from MFP in milk was also determined in preschool children by means of 24-hour F urinary excretion. In both studies F absorption was determined either under fasting conditions or when F ingestion occurred together with food intake. The results show that F absorption from MFP in milk is as high as that of NaF in water under fasting conditions and that the F bioavailability decrease from NaF in water is more important than that of MFP in milk when F ingestion occurs simultaneously with food intake.

Absorption↗
PubMed1994

Effect of various post-brushing activities on salivary fluoride concentration after toothbrushing with a sodium fluoride dentifrice.

The study consisted of eight experiments, divided into three series, aimed at investigating the effect on the salivary fluoride (F) concentration of three post-brushing regimes: (1) rinsing once or twice with water, (2) rinsing either with a slurry of the toothpaste foam and water or with an 0.05% NaF solution, or a single NaF mouthrinse with no prior brushing, and (3) chewing and drinking ('eating') for 2 min. Brushing was done with 1.5 g of an 0.32% NaF dentifrice. The concentration of F in whole saliva was determined in 15 subjects at various time points up to 45 min after completing each experimental procedure. Results showed that the initial (0 min post-brushing) F concentration in saliva decreased about 1-2 times after a single, and 4-5 times after a double post-brushing water-rinse, as compared with no rinsing at all (p < 0.001). Brushing followed by a mouthrinse with an 0.05% NaF solution elevated the F concentration more than brushing alone (p < 0.001). Rinsing with the slurry of toothpaste foam and water gave only a somewhat (but not significantly) lower concentration of F in saliva than just rinsing with the 0.05% NaF solution. Eating immediately after brushing reduced the salivary F level about 12-15 times (p < 0.001) compared with brushing alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

Fluoride concentrations and distribution in premolars of children from low and optimal fluoride areas.

We have compared the fluoride (F) concentrations from the enamel surface to the dentino-enamel junction (DEJ), and through dentine to the dentino-pulpal junction (DPJ) in premolars extracted from school children in Chemnitz (former Karl-Marx-Stadt), Germany (F: 1.0 ppm in the water supply), Erfurt, Germany (F: 0.2 ppm in the water supply) and Nagoya, Japan (F: 0.1 ppm in the water supply). In teeth from children in Cheminitz, Erfurt and Nagoya, the profiles of F distribution using an abrasive microsampling technique revealed high F concentrations in the enamel surface, with a substantial decrease towards a plateau in the interior. In dentine the F concentrations were higher than in enamel, and also decreased to a plateau from the DEJ, thereafter increasing considerably towards the DPJ. F concentrations at any depth in the enamel and dentine of teeth from Chemnitz were 2-3 times higher than those in Erfurt and Nagoya. There was no significant difference in F concentrations or distributions between Erfurt and Nagoya. Close to the DEJ in both enamel and dentine as well as the enamel surface and the DPJ side of dentine, higher F concentrations were observed in Chemnitz compared with Erfurt and Nagoya.

Adolescent↗
PubMed1976

Urinary fluoride levels of population groups consuming salts different in fluoride concentration.

The effect of urinary level of a prolonged consumption of table salts containing 200, 250 or 350 mg/kg of fluoride has been studied. Urinary F concentration was increasing with all the three kinds of salt. In the group of consumers using 200 and 250 mg F/kg salt the equilibrium has been reached, but the urinary F level was still below that observed in populations who are drinking water of 1 mg/l F concentration. The equilibrium in the 2--14-year age groups consuming 350 mg F/kg salt could not yet set in. It is concluded that even a mixture of 350 mg F/kg is not in excess of the optimum and is far from the tolerated limit. Thus, this latter mixture may be used for caries prevention in areas with F-deficient drinking water, although it may be still less than the optimum.

Adolescent↗
PubMed1999

Effect of amine fluoride-stannous fluoride containing toothpaste (Meridol) on plaque and gingivitis in adults: a six-month clinical study.

Treatments that aim to reduce the accumulation of bacteria on dental surfaces are considered today as the most efficient way of treating gingivitis and the resultant destruction of periodontal tissues. Mechanical plaque removal was found to be very effective in the control of gingival inflammation for most patients, but the supplement of toothpastes and mouthwashes with anti-plaque properties may benefit individuals with unperfected plaque control. The aim of the present study was to investigate the long-term effect of amine fluoride/stannous fluoride (AmF/SnF2) toothpaste on plaque levels and gingivitis in adults, as an additional measure to standard oral hygiene. One hundred and three adult subjects with gingivitis were divided into two randomised groups. One group used NaF toothpaste (control) and the second group AmF/SnF2 (Meridol) toothpaste. The subjects were examined every two months under double-blind conditions. The recorded parameters were plaque index (PlI), gingival index (GI) and bleeding on probing. The differences in PlI between baseline and the end of the study were statistically significant for both treatments, and no significant differences were found between the two treatment groups. There was a significant drop in GI between baseline and the concluding examination only for the AmF/SnF2 group, but the differences between the two treatment groups were not significant. A significant reduction in the percentage of bleeding sites during the six-month study period was found in the AmF/SnF2 group, but not in the control group. The results of the present study suggest that the long-term use of AmF/SnF2 toothpaste in adults may be of benefit to gingival health.

Adult↗
PubMed2004

Comparison of a dual-phase fluoride toothpaste containing calcium, phosphate, and sodium bicarbonate with a regular fluoride toothpaste on calculus formation.

This clinical study compared the effect on dental calculus formation of a dual-phase fluoride dentifrice containing sodium bicarbonate, calcium, and phosphate with that of a regular dentifrice using a short-term clinical model in which calculus formation was facilitated. A total of 87 adult volunteers completed this study, which was a double-blind, parallel-group design, consisting of 2-week pretrial and trial periods separated by a washout period. A partial-mouth technique was used wherein the lower anterior teeth were protected from brushing by a custom-fitted toothshield, which doubled as an applicator for an undiluted dentifrice, twice daily. Calculus was measured on the labial/lingual surfaces of six lower anterior teeth by the Volpe-Manhold Index (V-MI). Subjects used a non-tartar-control dentifrice during the pretrial period to determine calculus formation rates, and these V-MI scores were used as baseline data for random allocation to either a control or test product for the trial period. Subjects who were accepted into the study, based on existing tartar deposits, readily formed calculus during the pretrial period using the toothshield method. During the trial period, subjects who were assigned the test dentifrice had comparable amounts of calculus accumulation to those who used the control dentifrice. However, subjects in the test dentifrice group had significantly lower (16%) calculus scores on lingual surfaces than those in the control group. Intragroup comparisons of V-MI data from the pretrial period with those from the trial period provided similar overall results to the comparisons between groups. This study demonstrated that a dual-phase baking soda dentifrice containing calcium and phosphate did not increase calculus accumulation relative to a regular dentifrice when used by adults with a propensity for developing calculus.

Adult↗
PubMed2000

Toxicokinetics of intravenous fluoride in rats with renal damage caused by high-dose fluoride exposure.

Fluoride (F) complexes are used in some fields of industry and medicine. F excretion mainly depends on kidney function. Urinary F concentration is measured to monitor the health of workers exposed to F. The toxicokinetics of F were studied by analyzing plasma concentration of F after intravenous injection of 2.86, 5.71 and 8.57 mg/kg into male Wistar rats. A dose-response relationship was recognized between these F doses and renal tissue injury. Blood samples were removed at 0, 10, 20, and 30 min, and after 1, 2, 3, 4, 5, and 6 h after injection. Plasma concentration-vs-time profiles were evaluated by a nonlinear least-squares method for fitting data to polyexponential equations and calculation of relevant pharmacokinetic parameters. Results indicated that a two-compartment model could describe the elimination of F from plasma. The beta rate constant, total plasma clearance (C1) and first-order rate constants (K21, Kel) decreased, and the half-time of the beta-phase (t1/2beta) was significantly prolonged with increasing dose. The kidney is the main target organ for F toxicity. Acute exposure to high doses of F damages renal tissue and causes renal dysfunction. The C1 of F is mainly dependent on renal F excretion. Since severe kidney damage markedly affected the toxicokinetics of F and decreased its elimination, other nephrotoxic indicators and measurement of plasma F concentration are necessary for monitoring high-dose F exposure.

Analysis of Variance↗
PubMed1995

Proton microprobe assessment of the distribution of fluoride in the enamel and dentine of developing central incisors of sheep and changes induced by daily fluoride supplements.

Ten sheep were given 0.5 mg fluoride (F) and 10 sheep 0.2 mg F/kg body wt orally for periods of 1-6 months while 8 sheep received no additional F. One incisor from each sheep was sectioned longitudinally in the midline and, using the proton microprobe, multiple scans for calcium and F were made across the enamel and dentine. F was determined by proton-induced gamma-ray emission and calcium by X-ray emission. Tooth length and hence the stage of ameloblast activity for each of the 28 teeth at the start of the experiment was determined using a tetracycline marker. In addition, the stage of enamel development of the eight control teeth (no dietary F) at the time of their extraction was assessed from their macroscopic appearance. Continuous changes in F levels occurred in both enamel and dentine throughout tooth development and also in the mature enamel and associated dentine after ameloblast regression. All scans for all stages of tooth development and all F treatments showed a high F concentration at the enamel surface. Early in the secretory phase, a wide-based F peak occupied the entire width of the enamel with a similar F peak in the dentine. In the control teeth, no consistent increase in F concentration occurred at the enamel surface during later development. When F supplements were started early in the maturation phase an increase in F concentration only at the enamel surface was recorded. When F supplements were also given during the secretory phase, higher F concentrations were recorded not only at the enamel surface but also for the inner enamel and dentine plateau. These findings, based on a small number of sheep, indicate that further research is needed to clarify the method and control of F uptake and to determine the changes in these processes during the different stages of tooth development.

Amelogenesis↗
PubMed2004

The efficacy of a fluoride chewing gum on salivary fluoride concentration and plaque pH in children.

OBJECTIVES: The purpose of this study was therefore to study the influence of different chewing times on the salivary F concentration and on the recovery of plaque pH directly after a sucrose rinse on both the chewing and the non-chewing side. METHODS: For this purpose, one piece of sugar free chewing gum was chewed to 10 healthy subjects (aged 8-10 years, 5 male and 5 female children). Subjects refrained from toothbrushing for 3 days. On the fourth day, they rinsed for 1 min with 10 microl of a 10% sucrose solutions. After 8 min, chewing gum was given and started to chew for either 5, 10, 20, 30, 45 min or control (sucrose rinse). Thus, altogether six test sessions were repeated at one week intervals. Measurements of F concentration in saliva and pH of approximal plaque were carried out at two contralateral sites for up to 60 min. RESULTS: Higher salivary F concentrations were found on the chewing side than on the non-chewing side (expressed as) (p<0.05). But, the difference between the chewing and the non-chewing side was not obvious for the plaque pH (expressed as AUC) (p>0.05). Therefore, this study showed that: (1) the F concentrations in saliva after chewing a F containing chewing gum had only small numerical differences among the various chewing times, with the exception for 5 min. All chewing time periods showed statistically significant differences between chewing and non-chewing side. (2) The prolonged chewing time increased the plaque pH recovery after a sucrose rinse (p<0.05) but there was no statistically significant difference on both of the chewing and non-chewing side (p>0.05). CONCLUSION: The results of this study indicated that a prolonged chewing time was favorable to the plaque pH recovery after a sucrose rinse and, to a certain extent, to the salivary fluoride concentration. Also it was shown that the F concentration in saliva was strongly dependent on which side the subject chewed on.

Analysis of Variance↗