European Organization for Caries Research Workshop: Methodology for Determination of Potentially Available Fluoride in Toothpastes.

Toothpastes are the most universally accepted form of fluoride delivery for caries prevention. To provide anti-caries benefits, they must be able to release fluoride during the time of tooth brushing or post brushing into the oral cavity. However, there is no standard accepted procedure to measure how much fluoride in a toothpaste may be (bio) available for release. The European Organization for Caries Research proposed and supported a workshop with experts in fluoride analysis in toothpastes and representatives from industry. The objective of the workshop was to discuss issues surrounding fluoride analysis in toothpaste and reach consensus on terminology and best practices, wherever the available evidence allowed it. Participants received a background paper and heard presentations followed by structured discussion to define the problem. The group also reviewed evidence on the validity, reliability and feasibility of each technique (namely chromatography and fluoride electroanalysis) and discussed their strengths and limitations. Participants were able to reach a consensus on terminology and were also able to identify and summarize the advantages and disadvantages of each technique. However, they agreed that most currently available methods were developed for regulatory agencies several decades ago, utilizing the best available data from clinical trials then, but require to be updated. They also agreed that although significant advances to our understanding of the mechanism of action of fluoride in toothpaste have been achieved over the past 4 decades, this clearly is an extraordinarily complex subject and more work remains to be done.

Characterization of cornified oral mucosa for iontophoretically enhanced delivery of chlorhexidine.

Topical administration of chlorhexidine for periodontal disease can provide advantages over systemic delivery, but is limited by the permeability of the cornified oral mucosal tissue. In the present study, passive and iontophoretic transport of tetraethylammonium, salicylate, mannitol, dexamethasone, fluoride, and chlorhexidine across bovine palate was investigated to (a) determine the intrinsic barrier properties of bovine palate for its eventual use as a model of human cornified oral mucosa, (b) examine the feasibility of iontophoretically enhanced transport of chlorhexidine into and across bovine palate, and (c) identify the transport mechanisms involved in iontophoretic transport across the palate. The histology study suggests that bovine and human palates have similar cornified epithelium structures; bovine palate could be a model tissue of human hard palate for drug delivery studies. Transport study of tetraethylammonium, salicylate, and mannitol suggests that bovine palate was net negatively charged and the cornified epithelial layer was the rate-determining barrier. The direct-field effect (electrophoresis) was shown to be the dominant flux-enhancing mechanism in iontophoretic transport of ionic compounds. Electroosmosis also contributed to the iontophoretic transport of both neutral and ionic permeants. Anodal iontophoresis enhanced the delivery of chlorhexidine into and across the palate, reduced the transport lag time, and provided tissue concentration above the drug minimum inhibitory concentration, and therefore could be a promising method to assist in the treatment of periodontal disease.

Passive and iontophoretic transport of fluorides across enamel in vitro.

Passive and iontophoretic transport of fluoride from three fluoride sources, NaF, sodium monofluorophosphate (MFP), and SnF2 solutions, across bovine enamel was investigated to (1) determine the characteristics of the intrinsic barrier of enamel for ion transport, (2) examine the feasibility of iontophoretically enhanced transport of fluoride across enamel, and (3) identify the transport mechanisms involved in enamel iontophoresis. Conductivity experiments were performed with bovine enamel specimens in side-by-side diffusion cells to evaluate the electrical and barrier properties of the enamel with electrolytes of different ion sizes and under different ion concentrations and pH conditions in vitro. Transport experiments of the enamel were performed in the diffusion cells with the NaF, MFP, and SnF2 solutions. The conductivity results showed that the enamel specimens behaved as a neutral membrane or that of low pore charge density. Cathodal iontophoresis significantly enhanced the delivery of fluoride ions across the enamel from the solutions over passive transport, consistent with Nernst-Planck theory and the direct field effect (i.e., electrophoresis) as the dominant flux-enhancing mechanism. The enamel demonstrated significant transport hindrance for the ions, and the effective pore radii of the transport pathways in the enamel were found to be approximately 0.7-0.9 nm.

Protective effects of SnF2 - Part I. Mineral solubilisation studies on powdered apatite.

PURPOSE: To compare the ability of two active ingredients - sodium fluoride (NaF) and stannous fluoride (SnF2 ) - to inhibit hydroxyapatite (HAP) dissolution in buffered acidic media. METHODS: Two in vitro studies were conducted. HAP powder, which is representative of tooth mineral, was pretreated with: test solutions of NaF or SnF2 , 10 g solution per 300 mg HAP powder (Study 1); or NaF or SnF2 dentifrice slurry supernatants, 20 g supernate per 200 mg HAP powder for 1 minute followed by three washes with water, then dried (Study 2). About 50 mg of pretreated HAP was exposed to 25 ml of acid dissolution media adjusted to and maintained at pH 4.5 in a Metrohn Titrino reaction cell. Exposure of HAP to the media results in dissolution and release of hydroxide ion, increasing the pH of the solution. The increase in pH is compensated for by automatic additions of acid to maintain the original pH (4.5) of the reaction cell. Total volume of titrant added after 30 minutes was used to calculate the percentage reduction in dissolution versus non-treated HAP control. RESULTS: Both F sources provided protection against acid dissolution; however, in each study, SnF2 -treated HAP was significantly more acid-resistant than the NaF treated mineral. In study 1, at 280 ppm F, representing concentrations of F found in the mouth after in vivo dentifrice use, the reduction in HAP dissolution was 47.7% for NaF and 75.7% for the SnF2 -treated apatite (extrapolated). In study 2, the reduction in HAP dissolution was 61.3% for NaF and 92.8% for SnF2 -treated samples. Differences in percentage reduction were statistically significant (Paired-t test). CONCLUSIONS: Results of these studies demonstrate that both of the fluoride sources tested enhance the acid resistance of tooth mineral and that resistance is significantly greater after treatment with SnF2 compared with treatment of tooth mineral with NaF.

Chemometric evaluation of physicochemical properties of carbonated-apatitic preparations by Fourier transform infrared spectroscopy.

The purpose of this study was to develop a simple and quick method of evaluating the physicochemical properties of carbonated apatite preparations (CAP) as an index of the bioaffinity of implantable materials based on Fourier-transformed-infrared (IR) spectra by chemometrics. The wet-synthesized CAPs contained various levels of carbonate content (CO(3)), and were analyzed microstrain parameter (MS), crystallite size parameter (CP), specific surface area (Sw), CO(3), and solubility parameter (pK(HAP)) using by X-ray powder diffraction, nitrogen gas adsorption, IR, and UV absorption. The IR spectral results of CAPs suggested that the peak intensities of CAP reflected the physicochemical properties of the samples. The IR data sets were calculated to obtain calibration models evaluating the physicochemical properties of CAPs by a partial least squares regression analysis (PLS). As validation of the calibration model, physicochemical properties of CAP could be evaluated based on validation IR data sets of independent samples, and those values had sufficient accuracy. The regression vector of each calibration model suggested that the physicochemical properties of CAP, such as CO(3), Sw, MS, CP, and pK(HAP), were affected by phosphate, hydroxyl, and carbonate groups.

Influence of crystallite microstrain on surface complexes governing the metastable equilibrium solubility behavior of carbonated apatites.

This study was on the influence of the mineral phase crystallite microstrain (CM) on the nature of the surface complex (SC) governing the metastable equilibrium solubility (MES) behavior of carbonated apatites (CAPs) in aqueous acidic media (0.10 M acetate buffers, with and without fluoride, 0.50 M ionic strength maintained with NaCl). The MES behavior of a set of four CAPs (synthesized at 85 degrees C by a precipitation method) of increasing CM and therefore of increasing MES (CAP4 > CAP3 > CAP2 > CAP1) was quantified. The following were the findings. For CAP1 and CAP2, the SCs deduced were Ca10(PO4)6(OH)2 and Ca10(PO4)6F2 for the nonfluoride and the fluoride cases, respectively. For CAP3 and CAP4, the SCs deduced were Ca9.5(PO4)6OH or Ca9.5(HPO4)(PO4)5(OH)2 and NaCa9.5(PO4)6F2 for the nonfluoride and the fluoride cases, respectively. These results together with that from an earlier limited study show that the Ca/P ratio of the SC decreases from 1.67 to 1.58 to 1.50 with increasing CM of the CAPs; this relationship inversely correlates with the chemistry of maturation of aqueously precipitated defective apatites. Also the SCs do not appear to exist as a continuous series and only a few SCs may account for the MES behavior over a wide range of CAP preparations.

Stannous fluoride/sodium hexametaphosphate dentifrice increases dentin resistance to tubule exposure in vitro.

OBJECTIVE: The purpose of this study was to compare the reactivity of three dentifrice formulations on smear layer-covered root dentin surfaces, and the effects of the formulation treatments on resistance to acid softening and dentinal tubuli disclosure. METHODOLOGY: Commercial dentifrices, including Crest Cavity Protection Regular, Colgate Total, and a new dentifrice comprised of stannous fluoride/sodium hexametaphosphate (SnF2/HMP: Crest Pro-Health), were cycled through a pre-treatment period on smear layer-covered dentin surfaces, including intermittent soaking in dentifrice slurries and whole human saliva immersion. Following pre-treatments, the cycling treatments were modified to include dietary acid exposure, including soaks in an acidic soft drink. Vickers surface microhardness, variable pressure scanning electron microscopy (VP-SEM), and confocal laser scanning microscopy in reflection mode (CLSM) were used to characterize dentin reactivity and smear layer protection. RESULTS: CLSM and SEM analyses showed that specimens treated with SnF2/HMP appeared to resist acid solubilization, evidenced by the absence of disclosed dentinal tubuli. The histo-tomographic observations in this study were in agreement with the hardness measurements. The superior surface protection of dentin with SnF2/HMP would suggest potential benefits in ameliorating dentinal hypersensitivity in the clinical situation. CONCLUSION: A stannous fluoride/sodium hexametaphosphate dentifrice prevents dietary acid softening and tubule exposure of smear layer dentin surfaces.

A novel dentifrice technology for advanced oral health protection: A review of technical and clinical data.

Throughout the world, dentifrices have played a key role in the practice of good oral hygiene and promotion of better oral health. In addition to providing general dental cleaning, toothpastes also have served as an excellent vehicle for the introduction of new agents that deliver therapeutic and cosmetic benefits. Key examples of using dentifrices to provide added benefits include the introduction in 1955 of the first fluoridated toothpaste clinically proven to fight caries (Crest Cavity Protection) and the launch of the first tartar-control dentifrice (Crest Tartar Control) in the mid-1980s. To continue expanding the health and esthetic benefits offered by a single dentifrice, a multitude of agents have been investigated over the past 3 decades. The focus of these investigations has been in the multibenefit segment, the most widely used among US consumers.

Sustained antibacterial actions of a new stabilized stannous fluoride dentifrice containing sodium hexametaphosphate.

Stannous fluoride has been used as a chemotherapeutic agent for years to improve oral health. The benefits of stannous fluoride in controlling caries, plaque, and gingivitis are directly associated with its antimicrobial actions. Recently, a novel dentifrice was developed that combines stannous fluoride with an anticalculus agent, sodium hexa. metaphosphate. A series of independent evaluations were conducted to assess the long-lasting antimicrobial activity of stannous fluoride in the new stannous fluoride/sodium hexametaphosphate dentifrice: an in vitro Live/Dead assay; an in vivo Plaque Glycolysis and Regrowth Model study; a rapid in vitro salivary bacteria metabolic activity study; and a 12-hour in vivo tin-retention study. In the Live/Dead study, the new stannous fluoride/sodium hexametaphosphate dentifrice killed approximately 90% to 99% of the salivary microbes 16 hours after a single exposure. Similarly, the stannous fluoride dentifrice produced statistically significant reductions in plaque acid production and plaque regrowth activity compared to plaque treated with a standard fluoride dentifrice at all time intervals measured after product exposure (15 and 45 minutes). Results from the final two studies collectively demonstrated the presence of total soluble tin, which serves as a marker for the active stannous fluoride, at levels above the minimum concentration for inhibition of salivary bacteria metabolic activity 12 hours posttreatment. These findings confirm the long-lasting antibacterial action of the new stannous fluoride dentifrice, which serves as a basis for its therapeutic benefits.

Extrinsic whitening effects of sodium hexametaphosphate--a review including a dentifrice with stabilized stannous fluoride.

The number of tooth whitening products available to patients has grown dramatically during recent years. While peroxide is the primary agent found in products that bleach and remove intrinsic sources of discoloration, various ingredients are incorporated in formulations to remove and inhibit extrinsic sources of tooth discoloration, ie, tooth stain. Recently, an advanced antitartar ingredient with extrinsic-stain-inhibiting benefits was introduced: sodium hexametaphosphate. This long-chain condensed phosphate, also known as polypyrophosphate, chemically removes existing stains and provides long-lasting inhibition of new-stain chromogen adsorption. Sodium hexametaphosphate was originally introduced in a sodium fluoride dentifrice formulation and was later marketed in a chewing gum delivery system. Recently, sodium hexametaphosphate was launched in another dentifrice formulation containing stabilized stannous fluoride (Crest Pro-Health). This article reviews published clinical and laboratory data demonstrating sodium hexametaphosphate's extrinsic whitening benefits in all three formulations.

Laboratory studies on the chemical whitening effects of a sodium hexametaphosphate dentifrice.

Laboratory studies were developed to permit the evaluation of chemical actions of toothpaste components in the non-abrasive prevention and removal of tea stains. Powdered hydroxyapatites were used as substrates for adsorption of tea chromogens. Pre-treatment with a sodium hexametaphosphate dentifrice (Crest Dual Action Whitening) reduced tea adsorption to powdered apatite, while post-treatments of pre-stained powder resulted in desorption of tea components. These results exemplified the chemical actions of condensed calcium phosphate surface active builders toward dental stain removal and prevention. A cycling synamel chip model permitted the study of stain prevention, including salivary pellicle formation and chlorhexidine enhancement of dental staining by tea chromogens. Staining was evaluated by image analysis of color development. Under these conditions, condensed phosphate dentifrices were observed to produce superior prevention of stain accumulations, with Crest Dual Action Whitening dentifrice providing stain prevention superior to a variety of commercial dentifrices, including Colgate Total, Aquafresh Whitening, Colgate Tartar Control Whitening, Mentadent Baking Soda and Peroxide Whitening, Close-Up Whitening, Crest Tartar Control and Crest Regular Cavity Protection.

In vitro studies of the anticalculus efficacy of a sodium hexametaphosphate whitening dentifrice.

Laboratory studies involving crystal growth inhibition and plaque biofilm calcification were conducted to confirm the anticalculus potential of a dual-action whitening dentifrice containing sodium hexametaphosphate, a novel, enamel-safe, antitartar agent. Calcium hydroxyapatite crystal growth was significantly inhibited following direct supernate treatments by hexametaphosphate in solution and when formulated into the dual-action whitening dentifrice. Similarly, plaque biofilm calcification was significantly inhibited by supernate treatments of the hexametaphosphate whitening dentifrice. The activity of hexametaphosphate dentifrice in plaque biofilm calcification protocols exceeded that produced by commercial dentifrices containing polycarboxylic acid, metal ion and pyrophosphate tartar control ingredients. Results predict excellent clinical activity for hexametaphosphate dentifrice for the prevention of supragingival calculus formation. Published double-blind, randomized clinical studies confirm the validity of these laboratory models for the screening of potentially improved tartar control ingredients.

Hexametaphosphate effects on tooth surface conditioning film chemistry--in vitro and in vivo studies.

These studies compared the effects of Crest Dual Action Whitening dentifrice with sodium hexametaphosphate and control commercial dentifrices on the surface chemistry of conditioning film-coated dental enamel in vitro and in vivo. Conditioning film chemistry was studied by measurements of film thickness, ability to wet the surface/surface energy, conditioning film chemical composition and zeta potential. Laboratory and in vivo studies demonstrated that brushing and chemical-only treatment of pellicle-coated enamel surfaces produced marked changes in surface chemistry. Brushing of surfaces with all commercial dentifrices significantly reduced pellicle film quantity. Effects on non-brushed areas, of significance in the clinical situation, were different for different dentifrices. For dentifrice chemical treatments, calcium phosphate surface active builders, such as pyrophosphate and hexametaphosphate, produced stronger effects than standard (non-tartar control) dentifrices, peroxide baking soda dentifrices and dentifrices formulated with carboxylate polymers, viz. Colgate Total with copolymer. Crest Dual Action Whitening hexametaphosphate dentifrice removed more pellicle conditioning film, produced a lower zeta potential, produced the largest changes in film composition and had the greatest impact on surface free energies of the tested dentifrices. Crest Dual Action Whitening dentifrice also produced lasting changes in the reacquisition of pellicle conditioning film, as established by in vitro cycling immersion studies. Crest Dual Action Whitening dentifrice produced stronger and more lasting effects on surface film chemistry than low molecular weight pyrophosphate (Crest Tartar Control) or other polymeric-based dentifrice systems (Colgate Total). These surface chemistries may contribute to the unique clinical actions of hexametaphosphate established in recently reported, randomized clinical studies of tartar control, stain prevention and stain removal effects.