Retention Improvement in Fluoride Application with Cold Atmospheric Plasma.

This study aimed to apply fluoride formulations to enamel with cold atmospheric plasma (CAP) and analyze the fluoride uptake, retention, and acid resistance quantitatively. Human enamel specimens were divided randomly into 2 groups: group APF1, 1.23% acidulated phosphate fluoride (APF) gel; group APF2, 1.23% APF gel with CAP. Fluoride and CAP were applied to the samples 4 times at 1-wk intervals. The specimens were also stored in artificial saliva for 4 wk to evaluate the retention of fluoride. The fluoride content on the fluoride-treated enamel was measured by an electron probe microanalyzer. To detect the resistance to demineralization, the calcium-to-phosphate ratio of the enamel samples was measured after the application of APF gel with or without CAP, followed by soaking in the demineralization solution. In groups APF1 and APF2, the amount of fluoride detected increased depending on the application frequency, and more fluoride was detected in group APF2 than in group APF1. In the experiment examining the maintenance effect, fluoride was not detected in group APF1, whereas fluoride was detected in group APF2 up to the fourth week. As for the resistance to demineralization, the calcium-to-phosphate ratio of the enamel treated with APF and CAP was higher than that treated with APF alone, and it increased with the frequency of treatment. This study suggests that the combination treatment of CAP and fluoride improves retention of fluoride on the enamel and resistance to demineralization when compared with treatment with fluoride alone.

Impact of organic pollutants on metal and As uptake by helophyte species and consequences for constructed wetlands design and management.

Various industrial processes and anthropogenic activities in urban areas induce a release of metals, metalloids and organic pollutants. Phytoremediation of co-contaminated waters in constructed wetlands is a promising solution for reducing the impact on natural environments. In order to improve the design and management of constructed wetlands, more knowledge is needed concerning the effect of organic pollutants on plant metal and metalloid uptake. In this study, the effects of a mixture of organic pollutants commonly found in industrial effluents (hydrocarbons, polycyclic aromatic hydrocarbons, anionic detergent) on the uptake of ten metals and metalloids (MM), i.e. Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, by five helophytes having a wide European distribution were studied. Main effects of plant species and pollutant conditions on metal uptake and interactions between factors were determined by a statistical treatment of a microcosm experiment. Overall, the order of element uptake in plants was Fe > Al > Mn > Cr, Ni, Zn, > Cu > As, Cd, Pb, which was consistent with relative concentrations in the rhizosphere environment of microcosms. Larger amounts of metals were retained in belowground biomass of plants than in aboveground parts. Statistical analysis showed that organic pollutants enhanced the accumulation of Mn in whole plants and the retention of Fe in belowground parts, while they reduced the accumulation of Cd, Ni, and Zn in whole plants and the retention of Cu in belowground parts. For the other MM (Al, As, Cr, Pb), effects were variable, depending on the plant species. Among the five plants tested, Carex cuprina generally removed the highest quantities of MM, which was the result of both a high metal accumulation capacity and high biomass production. Nevertheless, no significant proportion of the MM total loading could be removed in plants' aboveground parts.

Studies on dental fluoride-releasing polymers. IV: Fluoridation of human enamel by fluoride-containing sealant.

An experimental fluoride-containing acrylic sealant was prepared using methacryloyl fluoride-methyl methacrylate copolymer as powder component. The in vitro fluoride acquisition by human enamel coated with the sealant after 11, 21, 41 and 84 days of incubation in a phosphate buffer of pH7 at 37 degrees C was determined. Fluoride penetration and uptake were increased by prolonging the exposure time of enamel to the sealant. Most of the fluoride retained in enamel was found to be present as fluorapatite. The discharge of fluoride in the sealant was about 12% of initial load after 84 days of immersion.

Topical fluoride therapy: discussion of some aspects of toxicology, safety, and efficacy.

Although ingestion of an acute toxic dose of fluoride is extremely rare in dental treatments, practitioners should be familiar with the signs and symptoms and with emergency measures of treating accidental overdosage. The amount of fluoride ingested chronically from the use of self-applied topical fluoride can be reduced to safe limits by instructing parents to dispense small amounts of toothpaste for their young children and to ensure that fluoride dentifrices and mouthrinses are fully expectorated. Similarly, when custom-fitted trays are used, only minimal amounts of fluoride gels are necessary. The minimal amount of such gels that can be dispensed appears to be influenced by their viscosity. Clinical efficacy does not support a reduction in the concentration of fluoride in commercial dentifrices.

Fluoride uptake and retention in vitro following topical fluoride applications.

Fluoride uptake and retention on maxillary and mandibular incisors were compared using a conventional APF gel, a thixotropic gel, and a new pluronic-based fluoride gel. Based on the results of in vivo acid-etch biopsies, significant fluoride uptake was obtained with each of the three agents. The highly viscous pluronic gel may provide an alternative to conventional topical fluoride gels for subjects--e.g., handicapped persons--with whom a tray system is not feasible.

Enamel silicon and fluoride relationships demonstrating a surface silicon effect that facilitates fluoride uptake.

This study indicated that a clear relationship exists between silicon and fluoride. We have also demonstrated a probable surface enamel silicon effect that increases fluoride uptake. The complex set of relationships described in the surface chemistry of calcium, tin, and zirconium with fluoride, hydroxide, phosphate, and other surface-occurring ions need not be considered to confuse the specific silicon-fluoride relationship presented here because in this computation we are relating the changes in the silicon and fluoride ion values only. We have, however, considered the thermodynamics of such reactions and intend to elaborate on it in a later publication. We are aware of the small depth of fluoride penetration into enamel after topical treatment Health Foundation, Research Unit at the National Bureau of Standards, Washington, DC 20034, USA.

Pharmacokinetic aspects of topical fluorides.

Pharmacokinetic studies have revealed quantitative information about the bioavailability, rate of absorption, distribution, and clearance of fluoride following the use of fluoride-containing dentifrices, gels, varnishes, and solutions. It is concluded that following the use of topical fluoride products, variable amounts of fluoride are swallowed and absorbed into the systemic circulation--amounts which may be sufficient to produce acute or chronic side-effects. Pharmacokinetic data should, therefore, form part of the basis for the optimal and safe use of fluoride products. In addition, there is a need for future research to determine the kinetics of fluoride in the oral fluids after the application of topical fluoride agents and to determine the associated changes in the composition of the mineral components of the oral fluids.

Clinical application of topical fluoride products--risks, benefits, and recommendations.

This portion of the symposium discusses the various methods of professionally applying high-concentration topical fluoride products and their risks and benefits. Numerous recent investigations in this area of research are reviewed and discussed. Data from these research investigations point to the need for care when high-potency F products are used, especially in young children. Oral-retained F doses following four-minute topical application procedures ranged from 10 to 31 mg when no suction devices or patient expectoration was utilized. Following the use of suctioning devices, oral-retained F doses ranged from 6 to 12 mg, a clinically unacceptable level. Following the use of suctioning devices plus patient expectoration, the oral-retained F doses were reduced to from 2 to 7.5 mg, depending on type of F product and application system. The following recommendation for topical application of high-potency F products are made: (1) No more than 2 g of gel per tray or approximately 40% of tray capacity should be dispensed. Even more conservative amounts should be considered for small children. (2) Because patients may have the need to swallow during a four-minute topical application procedure, the use of a saliva ejector during the procedure is recommended. (3) Following the four-minute application procedure, the patient should be instructed to expectorate thoroughly for from 30 sec to one min, regardless of whether high-speed suction is utilized. Expectoration is probably the single most effective way of reducing orally retained fluoride. (4) When utilizing custom individually fitted trays for patients requiring daily or weekly application of a high-F-concentration product, utilize only 5 to 10 drops of product per tray.

Topical fluorides: a discussion of risks and benefits.

Inadvertent ingestion of fluoride from topical procedures poses the risk of dental fluorosis in age-susceptible users. This risk can be minimized for mouthrinsing by restricting it to those above the age-susceptible limit. Operators administering topical fluoride treatments can take practical precautions that have been shown to reduce the amount of fluoride retained and, thus, reduce ingestion. Clinical and epidemiological studies have failed to establish that dentifrice ingestion by young children constitutes a serious fluorosis risk. Discussion of risk must consider the effect of perceived risks upon the public.

Titanium and fluoride concentrations in titanium tetrafluoride and APF treated enamel.

Greater fluoride concentrations were obtained in enamel treated with phosphate/fluoride solutions than in that treated with TiF4 at similar pH's (1.0) and F concentrations (0.6M F and 1.6M F). However, fluoride solution without added phosphate at pH 1.0 and 1.6M F concentration produced lower fluoride concentrations in enamel than in TiF4 treated enamel. It is proposed that in TiF4 treated enamal the fluoride uptake may be dependent upon the amount of Ti introduced into the enamel.

The biologic availability of fluoride from alginate impressions and APF gel applications in children.

Ten child volunteers received routine alginate impressions and APF gel topical applications during separate visits. Whole saliva, urine, and surface enamel fluoride concentrations were measured before and after these procedures. Significant increases in salivary, urinary, and enamel fluoride concentrations were observed following APF gel application but only in whole saliva following alginate impressions.

An in vitro model for assessment of fluoride uptake from glass-ionomer cements by dentin and its effect on acid resistance.

This investigation presents an experimental model for studying interactions of glass-ionomer cements (GICs) with bovine dentin slabs. Fluoride incorporation was studied with five serial abrasion biopsies, each being approximately 10 microns thick. The time of interaction was a very important parameter, indicating continuous fluoride release from the GIC and diffusion into dentin over a 30-day period. Expressed in mass per volume (mg F/cm3), the fluoride incorporation reached 12.0 mg at the first and 2.5 mg at the fifth layer, several times greater than the baseline of 0.27 mg/cm3 in bovine dentin. A subsequent test of acid resistance in a lactic acid buffer (pH 4.0), followed by microradiography of lesions, showed a characteristic 40-microns-wide acid-resistant zone on surfaces exposed to the GICs. In contrast, the untreated control surfaces had lesions demineralized evenly from the surface to the intact tissue, without the higher-density zone at the surface of the lesion. The model seems promising for screening fluoride incorporation into dentin from fluoride-releasing dental materials.

Fluoride uptake and caries rate in hamster molars after topical fluoride application followed by acidulation.

Daily topical application of 2% NaF on hamster molars for 4 days in vivo, followed by acidulation (grapefruit beverage, pH 3.3) resulted in a lower caries rate than NaF followed by water application. Fluoride uptake was somewhat higher, but not significantly so in the acidulated group.

Prevalence of dental fluorosis after fluoride-gel treatments in a low-fluoride area.

The goal of the present investigation was to study whether periodic use of fluoride-gel treatments resulted in an increased prevalence of dental fluorosis. 269 children, from 14 to 16 years of age, who had received semi-annual or quarterly fluoride-gel treatments were examined for possible fluoride-induced enamel changes. Further, in order to determine the amount of fluoride retained during the gel treatment, the expectorate was analyzed in 18 younger children presently participating in the prophylaxis program. It was found that the retention of fluoride averaged 7.3 mg per treatment (up to 0.5 mg fluoride per kg body weight). An increased prevalence of dental fluorosis was not observed, even after up to five yearly treatments were given during tooth formation periods. The background prevalence of dental fluorosis in a low-fluoride area in Denmark is described.

Effect of conditioning with fluoride and phosphoric acid on enamel surfaces as evaluated by scanning electron microscopy and fluoride incorporation.

The etching effect of 50% H-3PO-4 applied together with 2% NaF or SnF-2 was compared with the effect of H-3PO-4 on pre- and postfluoridated enamel by scanning electron microscopy. Substantial etching of enamel resulted with use of 50% H-3PO-4 with 2% NaF. High fluoride incorporation in the surface provided additional protection of the conditioned enamel.

Residual fluoride concentrations and scanning electron microscopic examination of root surfaces of human teeth after topical application of fluoride in vivo.

Fluoride concentrations in root surfaces of human teeth after a single topical application with a 2% acidulated sodium fluoride solution in vivo were investigated. Increased residual fluoride concentrations in the root surfaces and precipitations on the peritubular dentin, as revealed by SEM micrographs, may be factors in reducing hypersensitivity.

Predisposition to caries in hamsters following the Erosire effect of a commercial citrus beverage administered with and without supplemental fluoride.

A study was undertaken to investigate the effect of a citrus beverage on tooth erosion and predisposition to caries in hamster molars, and to determine if a supplement of 1.9 ppm fluoride to the beverage influences these systems. Results suggest that enamel erosion is a predisposing factor. The addition of physiological fluoride protects the enamel from erosion and caries.

Systemic absorption of fluoride from alginate impression material in humans.

Thirty minutes after routine alginate impressions in five adult subjects, plasma fluoride levels increased by an average of 2.6 times over control values. Urinary fluoride excretion rates increased approximately 2.9 times during the first two hours after the impressions. Average whole saliva fluoride levels at 15 minutes were over 100 times the average control concentration. When small amounts of alginate were deliberately ingested, plasma fluoride levels and urinary excretion rates increased sharply.

Improved fluoride incorporation and new in vitro fluorine elemental determination.

The CPA technique was shown to be very useful in nondestructively determining the concentration profiles of fluoride in extracted teeth. By means of this technique, it was found that in vitro treatment with K2ZrF6 incorporated substantially more fluoride into the enamel than NaF or APF by factors of 5 and more than 50, respectively. The concentration profile was determined from the tooth surface to a depth of 2.1 mum, with a resolution of 0.07 mum at the surface and 0.15 mum at a 2.1-mum depth. Proton-stimulated X-ray fluorescence was used to detect the elements heavier than Mg, for example, P, Cl, K, Ca, Ti, Fe, Ni, Ca, Zn, Zr, and Pb.

Fluoride deposition in human enamel in vivo from professionally applied fluoride prophylaxis paste.

Deciduous teeth were collected from children who received professional prophylaxis with an acidulated phosphate-fluoride (APF) or placebo paste and were analyzed to determine fluoride uptake. Enamel fluoride level was increased by the APF paste approximately 300 ppm at a depth of 2.5 micrometers during the first month after the prophylaxis was administered, after which it returned to pretreatment levels.