Method for the analysis of total fluoride in fluoride-releasing dental varnishes.

Today's fluoride-releasing varnishes (F-varnish) contain a wide variety of ingredients which present analytical challenges for measuring their total fluoride content. This study reports improved methods to measure fluoride content in F-varnishes. Six different commercially available F-varnishes that contain difluorosilane (0.1% F) or NaF (2.26% F) alone or in combination with calcium-phosphates were analyzed. In a vial, 1-3 drops (0.05-0.15 g) of varnish product was dispensed, dissolved in chloroform, equilibrated in TISAB and analyzed via fluoride ion-selective electrode. The average weight percentage of fluoride for all F-varnishes containing NaF ranged from 2.03 to 2.24% F, which is within 90% of the declared label concentration of 2.26% F. Analysis of the difluorosilane-containing product required an additional hydrolysis step. ANOVA found no significant difference between the 5% NaF varnishes at p < 0.05. This method for fluoride analysis yields reliable and reproducible results and can be used for a wide variety of F-varnishes. The standard uncertainty for this method is ±4%. This method may become the basis for national and international standards that ensure the F-varnish products used in clinical practice have the fluoride content declared in the product literature.

Total and free available fluoride in toothpastes in Brunei, Cambodia, Laos, the Netherlands and Suriname.

OBJECTIVES: This study assessed total and free fluoride concentrations in samples of toothpaste from Brunei, Cambodia, Laos, the Netherlands and Suriname, and investigated the labelling practices of the respective manufacturers. MATERIALS AND METHODS: Convenience samples were bought in the five countries and sent for analysis to the Netherlands. Levels of total and free available fluoride were measured. Details of the information declared on the packaging about type of fluoride and abrasives were recorded, and manufacturing and expiry dates were noted. RESULTS: A total of 119 samples of toothpaste were analysed. With one exception, all samples from the Netherlands complied with ISO (International Organisation for Standardisation) labelling requirements and there were no differences between the fluoride content declared and that found to be present on analysis. In samples purchased in the other countries, sodium monofluorophosphate (SMFP) toothpastes predominantly showed a low percentage of free available fluoride and the majority of toothpastes did not follow standard labelling guidelines. DISCUSSION: This study is not representative of any of the brands analysed, yet it highlights problematic discrepancies in products across countries. These may be related to the lack of a generally accepted methodology for analysing total and free fluoride content, absence of an agreement on the minimum concentration of fluoride required to ensure efficacy, weak regulating institutions that are unable to control labelling and consumer information, as well as a possible influx of counterfeit low-quality toothpaste. CONCLUSIONS: Renewed international focus should be directed towards closing gaps in guidelines and standards. Consumers should use only non-expired toothpaste, which should preferably be silica-based fluoride toothpaste that does not include abrasives containing calcium and that is properly labelled.

In vitro fluoride release and the antibacterial effect of glass ionomers containing chlorhexidine gluconate.

Fluoride release from glass-ionomers (GI) may be important for the prevention of secondary caries. The addition of chlorhexidine gluconate (CHX) to glass-ionomer cement (3%) adds an effect that enables it to be used as a varnish for the temporary coating of surfaces at risk for caries. This study investigated the fluoride release pattern and antibacterial effect of such a material. Glassionomer luting cement powder (Aqua-Cem) was mixed with water, 10% CHX or 10% CHX with 11% tartaric acid (TA), respectively, to test specimens (6 X 1.5 mm). After setting, the specimens were immersed in 10 ml deionized water and transferred to new vials after various intervals over a period of two months. The antibacterial effect towards mutans streptococci was assessed using agar diffusion. The fluoride release was measured after two hours and after shifting the specimens to new vials 10 times during the two-month period. The mean total fluoride release was 69.02, 50.64 and 48.56 microg/cm2 from each specimen in the GI, GI-CHX and the GI-CHX-TA groups, respectively. For two-hour old specimens, the mean inhibition zone was 0, 50, 36 mm2 in the GI, GI-CHX and GI-CHX-TA groups, respectively, and, after two months, 45 mm2 in the GI-CHX group and 19 mm2 in the GI-CHX-TA group. It can be concluded that the addition of CHX and CHX-TA adds antibacterial properties to GI and the release of fluoride is decreased.

Penetration of fluoride into natural plaque biofilms.

Caries occurs at inaccessible stagnation sites where plaque removal is difficult. Here, the penetration through plaque of protective components, such as fluoride, is likely to be crucial in caries inhibition. We hypothesized that topically applied fluoride would readily penetrate such plaque deposits. In this study, plaque biofilms generated in vivo on natural enamel surfaces were exposed to NaF (1000 ppm F-) for 30 or 120 sec (equivalent to toothbrushing) or for 30 min. Biofilms were then sectioned throughout their depth, and the fluoride content of each section was determined with the use of a fluoride electrode. Exposure to NaF for 30 or 120 sec increased plaque fluoride concentrations near the saliva interface, while concentrations near the enamel surface remained low. Fluoride penetration increased with duration of NaF exposure. Removal of exogenous fluoride resulted in fluoride loss and redistribution. Penetration of fluoride into plaque biofilms during brief topical exposure is restricted, which may limit anti-caries efficacy.

Fluoride stability in dentifrices stored in schools in a town of northern Brazil.

The aim of this study was to analyze fluoride stability in dentifrices stored during nine months in schools from Careiro da Várzea, State of Amazonas, Brazil. Analysis of total fluoride concentration, total soluble fluoride, and ionic fluoride in the dentifrice samples was performed in four different time periods: at the time of purchase (baseline); after three months, after six months, and after nine months of storage. Fluoride concentration was determined using a specific electrode (Orion 96-09) connected to an ion analyzer (Orion A-720) and calibrated with fluoride standard solutions containing 2.0 to 32.0 ppm F. The results obtained during the measurements were analyzed by analysis of variance (one-way ANOVA), followed by Tukey's test for comparison of the means. After nine months of storage, total soluble fluoride, the active form of fluoride, decreased by 21.9%. As total soluble fluoride was below the minimum required for anticaries efficacy (1,000 ppm F) in the fourth analysis, it may be concluded that anticaries potential decreased with storage time.

Rheology of fluoride gels.

A number of fluoride gels containing a hydroxyalkyl cellulose thickening agent show non-Newtonian rheological behavior in the form of stress thinning (apparent viscosity decreasing with shear rate). Viscosities of 450 to 780 poise at low rates of shear down to 1.0 to 2.0 poise at high rates of shear were obtained. The effect of temperature on viscosity was comparatively small. One gel, containing a noncellulosic thickening agent showed a much more pronounced stress thinning (7,500 poise at low rates). Furthermore, at low rates of shear this material showed pronounced elastic behavior. This may well be clinically advantageous.

Oral fluoride retention with thixotropic and APF gels and foam-lined and unlined trays.

Ten child volunteers each received four topical fluoride applications using different techniques. The amounts of fluoride applied, recovered from the mouth, and retained in the mouth were calculated for each treatment. The value of patient expectoration following topical F treatment was also evaluated. The tray system with an absorptive liner significantly reduced the amount of gross oral-retained fluoride (p less than 0.01). Expectoration following topical treatment with either an APF or thixotropic gel was a significant adjunct in reducing the net oral-retained F dose (p less than 0.01). When expectoration is done following a topical F treatment, a thixotropic gel may be an added advantage in reducing oral F retention and ingestion. We recommend that suction devices be used during a topical F treatment, but most importantly that the patient be requested to expectorate thoroughly following topical treatment.

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.

An evaluation of the use of professional (operator-applied) topical fluorides.

Application of fluoride solutions, gels, varnishes, and prophylaxis pastes is reviewed as well as the sequential APF/SnF2 office-rinse method. The most widely-used technique is with 1.23% APF gel (12,300 ppm F) in trays. Clinical results from this method are similar to those achieved with an APF solution of the same fluoride concentration. A professional APF gel/tray application need not be preceded by a prophylaxis, should last four min, and should not be followed by a water rinse for 30 min. Fluoride varnishes are newer topical fluoride agents, but their relative efficacy, compared with other proven caries-inhibitory methods, remains to be fully determined. In general, fluoride prophylaxis pastes have not been shown to inhibit caries; however, their use is justified by the ability of some to replenish fluoride lost from the abrasive action of the paste on tooth enamel. The sequential office-rinse method has not been tested in randomized clinical trials, and its use cannot be recommended.

Fluoride concentrations in plaque, whole saliva, and ductal saliva after application of home-use topical fluorides [published eerratum appears in J Dent Res 1993 Jan;72(1):87].

It is now well-accepted that the primary anti-caries activity of fluoride (F) is via topical action. The retention of F in the mouth after topical fluoride treatment is considered to be an important factor in the clinical efficacy of F. The purpose of this study was to evaluate F levels in ductal saliva, whole saliva, and pooled plaque after treatment with topical F agents intended for home use. Ten consenting adults, mean (SD) age 31.0 (8.2) years, participated in all aspects of the study. Two days before each test, subjects received a professional tooth cleaning and subsequently abstained from all oral hygiene procedures to permit plaque to accumulate, and from the use of F-containing dental products. Treatments consisted of a placebo dentifrice (PD), fluoride dentifrice (FD; 0.24% NaF), fluoride rinse (FR; 0.05% NaF), and fluoride gel (FG; 1.1% NaF). Unstimulated whole saliva and pooled plaque were sampled at multiple points over a 24-hour period. In a separate experimental series, stimulated parotid saliva was sampled over a two-hour period after treatment. Fluoride levels generally followed the same pattern in whole saliva and pooled plaque samples, with FG > FR > FD > PD. Night-time F application resulted in prolonged F retention in whole saliva but not in plaque. Fluoride levels in parotid saliva were only slightly higher after F treatment and returned to baseline levels within two h. The results of this study indicate that the method of F delivery, the F concentration of the agent, and the time of application (daytime vs. night-time) are important factors influencing F levels in the mouth.(ABSTRACT TRUNCATED AT 250 WORDS)

Composition of fluoridated dental enamel studied by x-ray photoelectron spectroscopy (ESCA).

A combination of ESCA and argon-ion etching has been shown to be effective in determining the surface and subsurface composition of dental enamel. The heavy organic coating on enamel has been investigated. Beneath this coating, untreated enamel was found to have invariant phosphorus and calcuim concentrations over the region surface. The surface of enamel treated with an acid phosphate-fluoride gel was shown to be almost entirely connected to calcium fluoride. A phosphate species, noncalcium and possibly a sodium salt, was found to be present in the surface layer. At a depth lower than about 60 nm, there was a gradual increase in phosphorus concentration that approached the value for untreated enamel with increasing depth. The increasing phosphorus and decreasing fluorine concentrations were primarily caused by the increasing concentration of unreacted hydroxyapatite. These results have shown that ESCA coupled with argon-ion etching, can be used effectively to examine the surface and subsurface composition of dental enamel. The surface sensitivity, ability to strip thin layers of material, sensitivity to low atomic weight elements, and ability to differentiate between different oxidation states makes a combination of these two techniques extremely useful for dental research.

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.

Enamel fluoride uptake and retention from intensive APF gel applications in vivo.

Children, in the fifth school grade (mean age 11 years) in a fluoridated water area, self-applied acidulated phosphate-F gel (1.2% F) in custom-fitted mouthpieces on 5, 10, or 25 consecutive school days. Enamel F uptake, penetration, and retention were determined from analysis of 1,257 deciduous teeth exfoliated during and after the applications. F penetrated to 200 micrometer in enamel exposed to 25 applications of the gel and increased approximately 2,600 ppm at a 5 micrometer depth. Concentrations of F declined for approximately eight months after which levels stabilized, resulting in a 1,600 ppm increase of firmly bound F.

Spectrophotometric determination of fluoride in dosage forms and dental preparations.

The method is based upon the reaction between fluoride ions and the coloured complex of Fe(III) with methyl salicylate to form the stable, colourless hexaflouride complex of iron. The conditions of the method (pH, time and combination ratio) were studied and a standard curve was obtained for 0.01-0.08 mg NaF ml-1, at 525 nm. A study was conducted on interference with complexing anions of Fe(III), cations that react with fluoride ions and with common ingredients of dosage forms and dental preparations. The method was validated and the results showed good precision (100.16 +/- = 2.33%) comparable with that of other analytical methods. Good results were obtained in the spectrophotometric determination of fluoride ions in a stomatological gel and in a toothpaste.

Clinical evaluation of an intraoral device for the controlled release of fluoride.

An intraoral-releasing device designed to release 0.5 mg of fluoride per day was evaluated in a one-month trial. The results showed that the 11 men who wore the fluoride-releasing device on their maxillary first molars had significantly elevated levels of fluoride in their saliva and plaque compared with baseline levels. No significant changes were observed in mean serum or urine fluoride levels or in the gingival or plaque indexes during the study. The prevalence of S mutans in whole saliva did not change during the study and the relative proportion of S. mutans, S. sanguis, and A viscosus and A naeslundii in plaque also remained relatively stable. The elevated fluoride levels in saliva and plaque are presumptive evidence that the intraoral fluoride-releasing device could exert a cariostatic effect in humans. However, long-term clinical trials are needed to determine the cariostatic potential of this fluoride releasing system.

Assessing fluoride concentration uniformity and fluoride release from three varnishes.

BACKGROUND: The authors investigated the fluoride content uniformity of three commercial fluoride varnishes, as well as their fluoride-release behaviors. METHODS: The authors examined 20 doses from each of two tubes of Duraphat (Colgate-Palmolive Co., New York) and Duraflor (Pharmascience Inc., Montreal), and 20 doses of individually packaged 0.25-milliliter and 0.40-mL units of CavityShield (OMNII Oral Pharmaceuticals, West Palm Beach, Fla.). Part of the dose was dissolved in chloroform, followed by fluoride extraction with distilled water. The authors painted the remaining varnish from five predetermined doses from each group onto plastic substrates for examination of fluoride release. Fluoride concentrations in the solutions were measured with a fluoride-selective ion electrode. RESULTS: One-way analysis of variance showed statistically significant differences between varnish groups. The fluoride content was more uniform in Duraphat and CavityShield than it was in Duraflor. The fluoride release profiles in terms of percentage of total fluoride released over time were different among different groups of varnishes and were similar among samples from the same test group. The authors found that Duraflor released consistently more fluoride in artificial saliva than did the other two varnishes. CONCLUSIONS: Fluoride content can vary between doses dispensed from the same tube. Uniformity also varies between different varnishes and affects the retention of fluoride in the varnish. CLINICAL IMPLICATIONS: Clinicians should be aware that the nonuniform appearance of fluoride varnish as squeezed out of the tube could indicate separation of ingredients, resulting in variation of fluoride content.

Physical properties of proprietary light-cured lining materials.

Physical parameters of four photopolymerized lining materials were evaluated for comparative purposes and to contribute to the understanding of these novel materials. Properties investigated included compressive, diametral and flexural strength, modulus of elasticity, fluoride and calcium release for four weeks, and pH values for 24 hours. In general Cavalite and TimeLine were significantly stronger than Vitrabond and XR-lonomer and were essentially neutral in pH. All the materials exhibited a yield upon compressive strength testing. The fluoride release was intermediate for TimeLine and negligible with Cavalite. Vitrabond and XR-lonomer released significant amounts of fluoride at all time periods. XR-lonomer was the only material investigated to have significant calcium release, and this may have been related to its visible dissolution in water. This material also showed a low initial pH of 2.2. It, along with Vitrabond, demonstrated a gradual increase in pH over time. The behavior of TimeLine and Cavalite is therefore more consistent with that of a modified composite resin, whereas Vitrabond and XR-lonomer are similar in nature to glass-ionomer liners.

Abnormally high fluoride levels in commercial preparations of 40 per cent silver fluoride solution: contraindications for use in children.

Although a 40 per cent solution of silver fluoride would be expected to contain 6 per cent fluoride (60,000 ppm), F-levels of 100,000 ppm and 120,000 ppm were found in 14 commercial samples analysed at The University of Western Australia in 1993 and 1994. To determine whether F-levels in 40 per cent AgF preparations have remained high, the present investigation was aimed at analysing different batches of commercial preparations obtained more recently. Fluoride ion analysis was carried out on 24 AgF samples using the Ion-Selective Electrode technique. Independent analyses of the same samples were carried out by a private chemical testing laboratory (Genalysis). Ten samples supplied by Agson Chemical Export were found to contain between 75,000 and 100,000 ppm F-: Genalysis reported 80,000 to 120,000 ppm. Fourteen samples supplied by Southern Dental Industries were found to contain between 70,000 and 120,000 ppm F-; Genalysis reported 88,000 to 108,000 ppm F-. These results confirm significantly higher than expected F-levels (ANOVA p < 0.05) in commercial preparations of 40 per cent AgF. The solutions tested were found to contain a mixture of ammonium fluoride, sodium or potassium fluoride, and silver fluoride. The additional presence of silver difluoride and hydrofluoric acid resulting from the manufacturing process has been suggested as an explanation for the much higher than expected levels of fluoride ion. In view of possible toxicity of 40 per cent AgF in young children, it is concluded that such a highly concentrated solution should not be used clinically; instead, lower strength AgF solutions should be investigated for their efficacy in caries treatment.

Fluoride varnish concentration gradient and its effect on enamel demineralization.

PURPOSE: Two of the 4 fluoride varnishes available on the American market today are sold in 10-mL tubes of 5% NaF varnish (Duraphat and Duraflor). Pilot studies have shown that a separation of contents within these tubes exists. The purpose of the current study was 4-fold: (1) to measure the fluoride concentration gradient in 10-mL tubes of fluoride varnish, based on resting position of the tube prior to use; (2) to compare and contrast fluoride concentration gradients of Duraphat, Duraflor, and CavityShield; (3) to compare this gradient to the ability to inhibit caries in an artificial caries environment; and finally, (4) to determine if quantitative light fluorescence (QLF) can detect differences in lesions developed when exposed to an artificial caries environment and fluoride varnish. METHODS: Human teeth specimens were subjected to a caries challenge and treated with a sample of fluoride varnish from 1 of 5 categories: Duraphat stored horizontally and vertically for 1 week, Duraflor stored horizontally and vertically for 1 week, or a CavityShield 0.4 mL "unidose." All specimens were then analyzed with the QLF system and with confocal microscopy. RESULTS: Results showed no significant fluoride ppm differences exist between groups (P=.29). It was shown that the order in which Duraflor varnish was dispensed from tubes significantly affected the fluoride concentration (P<.05). The order effect was not significant for Duraphat (P=.99). QLF data analysis showed there was no significant difference (P>.05) in the amount of remineralization obtained by using any varnish stored in any position. CONCLUSIONS: These results indicate that all 3 brands of fluoride varnish are able to remineralize incipient in vitro carious lesions, regardless of what part of the 10-mL tube the varnish is taken from. However, a fluoride concentration gradient exists in tubes of Duraflor. Also, QLF is able to detect demineralized and remineralized incipient lesions.

Clinical evaluation of new designs for intraoral fluoride-releasing systems.

PURPOSE: Intraoral fluoride-releasing (IFR) devices provide elevated levels of fluoride in the mouth for extended periods of time. However, retention and protection of the devices have posed major challenges for clinical applications. The objectives of this study were to develop new methods for retaining and protecting IFR devices in the mouth and to assess their effects on salivary fluoride levels and distribution in adolescents. METHODS: Four different IFR systems (combinations of an IFR device and its retainer) were evaluated in four groups of 10 adolescents each, 12-15 years of age, for a period of six months. Each child wore two IFR systems of a given type affixed to the buccal surface of each permanent maxillary first molar. Unstimulated saliva samples were collected at each clinical examination and analyzed for fluoride. RESULTS: A significant increase in salivary fluoride concentration from a baseline mean of 0.07-0.69 microgram/mL was observed on day 14 postinsertion. IFR system retention was 85% after 6 months and, of the systems retained, 100% were functional. CONCLUSIONS: These findings suggest that IFR devices can be successfully protected and retained in the mouth for prolonged periods of time.