A study of radiogallium aqueous chemistry: in vitro and in vivo characterisation of (67) Ga-hydrolysed-stannous fluoride particles.

The objective of this study was to explore the aqueous chemistry of gallium using (67) Ga-chloride starting material, by radiolabelling hydrolysed(h)-stannous fluoride particles and then characterising the optimal formulation for radiochemical purity (RCP) and radioactive particle size distribution in vitro. The pilot reactions determined stannous fluoride was added to (67) Ga-acetate under nitrogen and then heated at 100 °C for 20 min to achieve ≥95% RCP and (67) Ga-particles were >3 µm in diameter. A high radioactive concentration of (67) Ga-h-SnF2 particles could be prepared similarly in ≥97% RCP with 74% as 3-5 µm and 26% >5 µm in diameter. The latter formulation had larger particles than (99m) Tc-h-SnF2 colloid (96% of 1-3 µm), and it resulted in a rat biodistribution of 41% in the lungs, 41% in the liver plus spleen and 18% in the carcass at 20 min after injection. The carcass activity was attributed to bone marrow and some (67) Ga-transferrin formed in blood. Isolated mixed human leucocytes were radiolabelled with (67) Ga-h-SnF2 particles in 100% efficiency, and the (67) Ga-cells did not release soluble (67) Ga(3+) at room temperature over 3 h. The (67) Ga-h-SnF2 particle formulation could find a use in labelling leucocyte cells for in vivo homing studies when delayed animal imaging is required.

Comparison of the incipient lesion enamel fluoride uptake from various prescription and OTC fluoride toothpastes and gels.

OBJECTIVE: The objective of this in vitro study was to compare the fluoride uptake into incipient enamel lesions of a novel 970 ppm F- ion SnF2 over-the-counter (OTC) gel (Enamelon Preventive Treatment Gel) and a novel 1150 ppm F- ion OTC toothpaste (Enamelon), each delivering amorphous calcium phosphate (ACP), to the uptake from two different prescription strength, 5000 ppm F- ion dentifrices containing tri-calcium phosphate (TCP) and a prescription 900 ppm F- ion paste containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). METHODS: The test procedure followed method #40 in the US-FDA Anticaries Drug Products for OTC Human Use, Final Monograph testing procedures. Eight sets of twelve incisor enamel cores were mounted in Plexiglas rods and the exposed surfaces were polished. The indigenous fluoride levels of each specimen were determined prior to treatment. The treatments were performed using slurries of a negative control (water) and the following products applied to a set of sound enamel cores: 5000 ppm F- ion, sodium fluoride (NaF) prescription (Rx) dentifrice "A" containing TCP; 5000 ppm F- ion, NaF Rx dentifrice "B" containing TCP; 900 ppm F- ion, NaF Rx paste with CPP-ACP; 1150 ppm F- ion, NaF OTC toothpaste; 1150 ppm F- ion, stannous fluoride (SnF2) OTC toothpaste delivering ACP (Enamelon); 1100 ppm F- ion, SnF2 OTC toothpaste; and 970 ppm F- ion, SnF2 OTC gel delivering ACP (Enamelon Preventive Treatment Gel). The twelve specimens of each group were immersed into 25 ml of their assigned slurry with constant stirring (350 rpm) for 30 minutes. Following treatment, one layer of enamel was removed from each specimen and analyzed for fluoride and calcium. The pre-treatment fluoride (indigenous) level of each specimen was subtracted from the post-treatment value to determine the change in enamel fluoride due to the test treatment. RESULTS: The increase in the average fluoride uptake for treated enamel cores was: 10,263 ± 295 ppm for the 970 ppm F- ion, Enamelon Preventive Treatment Gel; 7,016 ± 353 ppm for the 1150 ppm F- ion Enamelon Toothpaste; 4,138 ± 120 ppm for the 5000 ppm F- ion, NaF prescription dentifrice "A" with TCP; 3801 ± 121 ppm for the 5000 ppm F- ion, NaF prescription dentifrice "B" with TCP; 2,647 ± 57 ppm for the 1100 ppm F- ion, SnF2 OTC toothpaste; 1470 ± 40 ppm for the 1150 ppm F- ion, NaF OTC toothpaste; and 316 ± 9 ppm for the 900 ppm F- ion, NaF paste with CPP-ACP. The differences among all the products tested were statistically significant (p < 0.05), except for the two 5000 ppm F- ion products with TCP that were not statistically different from one another, and the 900 ppm F ion, NaF paste with CPP-ACP that was not statistically different from the negative water control. CONCLUSION: The Enamelon products (970 ppm and 150 ppm F ion, SnF2OTC dentifrices) delivering ACP provide statistically significantly more fluoride to incipient enamel lesions than two prescription strength 5000 ppm F- ion toothpastes containing TCP, the 900 ppm F- ion prescription paste containing CPP-ACP, and the other OTC toothpastes compared in this study.

Retention of antimicrobial activity in plaque and saliva following mouthrinse use in vivo.

The aim of this study was to determine the contribution of plaque and saliva towards the prolonged activity, also called substantivity, of three antimicrobial mouthrinses (Listerine®, Meridol®, Crest Pro Health®), used in combination with a toothpaste (Prodent Coolmint®). Volunteers brushed for 4 weeks with a toothpaste without antimicrobial claims, while during the last 2 weeks half of the volunteers used an antimicrobial mouthrinse in addition to brushing. At the end of the experimental period, plaque and saliva samples were collected 6 h after oral hygiene, and bacterial concentrations and viabilities were determined. The contribution of plaque and saliva towards substantivity was assessed by combining plaque obtained after mechanical cleaning only with plaque and saliva obtained after additional use of an antimicrobial rinse. Subsequently, resulting viabilities of the combined plaques were determined. The viabilities of plaque samples after additional rinsing with mouthrinses were lower than of plaque obtained after mechanical cleaning only, regardless of the rinse involved. Moreover, plaque collected 6 h after rinsing with antimicrobial mouthrinses contained a surplus of antimicrobial activity. Only Listerine showed decreased viability in saliva, but none of the mouthrinses showed any residual antimicrobial activity in saliva. The findings indicate that plaque left behind after mechanical cleaning contributes to the prolonged substantivity of antimicrobial mouthrinses.

Fluoride uptake from in situ brushing with a SnF2 and a NaF dentifrice.

Fluoride uptake into decalcified human enamel was determined from in situ brushing with a 0.40% SnF2-calcium pyrophosphate abrasive dentifrice, a 0.243% NaF-silica abrasive dentifrice, and a non-fluoride-silica abrasive placebo dentifrice. Dentifrice treatments were compared using a randomized block test design with 11 panelists, wearing specially fabricated partial dentures that were able to hold two 3-mm-diameter enamel discs in proximal positions. The enamel discs were analyzed for fluoride after two wk of regular use of the test dentifrices. The mean fluoride contents after use of the test dentifrices were 16.0, 8.4, and 4.6 micro/cm2 for the 0.243% NaF, the 0.40% SnF2, and the placebo dentifrice, respectively. The differences in the means were statistically significant. These uptake results correlate well with the reported clinical efficacies of these dentifrices.

Effect of temperature of SnF2 solution on tin and fluoride uptake by bovine enamel.

The tin and fluoride concentrations in surface layers of intact enamel specimens were analytically determined after treatment with 8% SnF2 solutions at temperatures of 25, 45, 65, and 85 C. Significant increases in fluoride uptake and particularly tin uptake in enamel correlated directly with the temperature of the SnF2 treatment.

Fluorine and tin uptake by enamel studied by x-ray photoelectron spectroscopy (ESCA).

ESCA has been combined with argon-ion etching to obtain depth profiles for SnF2-treated enamel. Three zones of products from the topical treatment are detected: a layer of tin oxide on the surface; fluoroapatite + hydroxyapatite at depths below about 0.2 micron; an intermediate layer CaF2, Sn(OH)2, Sn2PO4OH, and fluoroapatite between the two. Sn3F3PO4 was not detected.

Effects of two fluoride gels on fluoride uptake and phosphorus loss during artificial caries formation.

Blocks of human enamel were cycled through a demineralization--F-treatment-remineralization procedure and then analyzed for fluoride and the presence of caries-like lesions. Treatments with a sodium fluoride gel (5000 ppm F) increased the enamel fluoride concentration to 6500 ppm F, whereas a stannous fluoride gel (1000 ppm F) increased enamel fluoride to about 1200 ppm F. Although a control treatment (water) allowed caries-like lesions to form, as observed by microradiography, no lesions were found in either of the fluoride-treated groups. When the experiment was repeated with radioactive teeth, mineral loss, as determined by release of 32P, was again greatest in the water-treated control group, but some loss was observed in the fluoride treatment groups. The least loss was found in the sodium fluoride group. It was concluded that the fluoride treatments not only increased enamel resistance but also enhanced remineralization so that calcium phosphate was replaced during the subsequent remineralization phase. Because of the probability that stannous ions were deposited during the stannous fluoride treatments, some of the apparent calcium phosphate re-deposition in this group was probably stannous compounds.

Tin(II) fluoride vs. tin(II) chloride--a comparison of their coordination chemistry with neutral ligands.

Reaction of SnF2 in MeOH with the appropriate neutral N- or O-donor ligands produces [SnF(2,2'-bipy)]2SnF6, [SnF(1,10-phen)]2SnF4 and [SnF2(L)] L = Me3PO, dmso or pyNO). The X-ray structures of [SnF(2,2'-bipy)]2SnF6, [SnF(1,10-phen)]2SnF4 and [SnF2(dmso)], reveal trigonal pyramidal Sn(II) cores with longer fluorine bridges completing distorted 5- or 6-coordination. Attempts to prepare SnF2 adducts with various phosphine or diphosphine ligands in MeCN failed, whilst in CH2Cl2 solution complex reactions involving the solvent occurred. The NHC, 1,3-(2,6-di-isopropylphenyl)imidazol-2-ylidene (IDiPP) and SnF2 produced the imidazolium salt, [IDiPPH]SnF3, the crystal structure of which revealed the first example of a discrete trifluorostannate(II) ion. In contrast, diphosphine complexes of tin(II) chloride formed readily, including [SnCl2{Me2P(CH2)2PMe2}], [SnCl2{o-C6H4(PMe2)2}], [SnCl2{o-C6H4(PPh2)2}] and [(SnCl2)2(µ-Ph2P(CH2)2PPh2)], which were characterised by X-ray crystallography. The structures of [SnCl2{Me2P(CH2)2PMe2}] and [SnCl2{o-C6H4(PMe2)2}] reveal chloride-bridged dimers, but [SnCl2{o-C6H4(PPh2)2}], although also dimeric, has very asymmetric diphosphine coordination best described as κ(1). The structures of [(SnCl2)2(µ-Ph2P(CH2)2PPh2)] and of [SnCl{o-C6H4(AsMe2)2}]SnCl3 reveal trigonal pyramidal cores, but with longer Sn···Cl bridges affording polymeric structures. The synthesis of [SnCl2(R3EO)2] (R = Ph, E = P or As; and R = Me, E = P) are also reported, along with the structure of [SnCl2(Me3PO)2], which contains distorted tetragonal pyramidal Sn(II) coordination. X-ray structures are also reported for [(PMe3)2CH2][SnCl3]2 and [Ph2P(H)(CH2)2P(H)Ph2][SnCl3]2, obtained as by-products from the attempts to synthesise phosphine complexes, as well as [(o-C6H4(PMe2)2CH2]I2. All complexes were characterised by microanalysis, IR and multinuclear NMR spectroscopy ((1)H, (19)F{(1)H}, (31)P{(1)H } and, where solubility allowed, (119)Sn). Comparisons are drawn with corresponding Sn(IV) and Ge(II) complexes.

Acid resistance of enamel exposed to fluoride-containing orthodontic cements.

In a previous study enamel fluoride uptake from fluoride-containing orthodontic cements was evaluated after a 21-day period. The enamel fluoride uptake from a zinc phosphate cement (A), a zinc phosphate cement containing 5 per cent stannous fluoride by weight (B), and a silicophosphate cement (C) was compared. The results indicated that there was a net loss of fluoride from enamel beneath the orthodontic bands cemented with A while the enamel beneath B and C acquired significant amounts of fluoride. The purpose of the present study was to evaluate enamel fluoride uptake after 12 weeks and the effect of the fluoride uptake or loss by the enamel on acid resistance. Five teeth each had bands cemented with cements A, B and C, respectively, and were individually suspended in synthetic saliva for 12 weeks at 37 degrees C. Following this period the bands were removed, the cements were carefully cleaned off the teeth, and the crowns of the teeth were individually suspended in a lactic acid buffer at pH 4 for 4 weeks. Each tooth crown was then sectioned longitudinally and examined microradiographically to study the degree of enamel demineralization. Characteristic subsurface enamel carieslike lesions were noted on all the specimens studied. The carieslike lesions in the enamel exposed to the fluoride-containing cements were considerably reduced. The enamel which had acquired fluoride from the fluoride-containing cements was apparently more resistant to artificial caries attack.

Fluoride deposited by topical applications with stannous fluoride in human enamel.

The aim of this study was to quantify the fluoridating effect of a 4% aqueous solution of SnF2 applied for 5 min. and 30 min. resp., and to measure the amounts of KOH soluble fluoride and acquired fluoride separately (APF gel data being included for comparison). Blocks of intact enamel were treated with the topical agents and subsequently exposed to 1 M KOH solutions for 24 h. No significant amount of fluoride was dissolved from control specimens by this treatment. Subsequently, the acquired F in the enamel was determined by the acid etch technique. The amount of fluoride in the KOH solutions after 5 and 30 min. SnF2 application are comparable : 6.2 and 7.4 micrograms . cm(-2) resp. A single topical treatment of SnF2 of 5 and 30 min. did not produce a significant enrichment of fluoride in the enamel. The considerable accumulation of fluoride reaction products on the outer enamel surface was only 1/3 of the amount deposited by APF gels.

The effect of stannous fluoride on human plaque acidogenicity in situ (Stephan curve).

A system employing an Ingold glass electrode was shown to give reliable measurements of pH drops in dental plaque in situ (Stephan curve readings). The system was used to demonstrate that mouthrinses of 0.2 per cent aqueous solutions of stannous fluoride reduced the pH drops markedly for at least seven hours. A reduction of the stannous fluoride concentration increased the pH drops and decreased the duration of the inhibiting effect. A commercial toothpaste containing stannous fluoride and stannous pyrophosphate had an effect similar to the 0.2 per cent mouthrinse. It was shown that tin accumulated in dental plaque after application of solutions containing stannous fluoride. About 40 per cent of the amount of tin present in the plaque immediately after the mouthrinse was still retained seven hours later. It is suggested that the reduction in acid formation may be caused by stannous ions adsorbing to the bacterial cell wall thus disturbing membrane transport mechanisms, or through inhibition of enzyme systems essential in the fermentation of sugars. The observed effect may be a part of the mechanism involved in the caries preventive function of stannous fluoride.

[Effects of tin on rats. II. Comparison of the effects of tin (II) chloride and yeast-incorporated tin]. / Zinnwirkung auf Rattan. 2. Mitt. Vergleich der Wirkung von Zim(II)-chlorid und in Hefe inkorporiertem Zinn.

After application of SnCl2 and tin incorporated into baker's yeast, the effects on carbonic anhydrase (CA), glutathione peroxidase (GPx), lactate dehydrogenase (LDH), alkaline phosphatase (AP) and leucine aminopeptidase (LAP) were measured. The tin contents of liver and kidneys were determined. CA and GPx are not affected. AP and LAP are inhibited by high concentrations of tin (as SnCl2). Tin incorporated into yeast exerts no effect. Inorganic tin produces increases in liver and kidneys.

The effect of some metal ions on volatile sulfur-containing compounds originating from the oral cavity.

Halitosis originates mainly from the oral cavity, and the volatile sulfur-containing compounds (VSC) are the major contributors of the unpleasant odor. Anaerobic G- bacteria use sulfur-containing amino acids in their production of VSC. Zinc has been shown to inhibit production of odiferous VSC, and the mechanism proposed has been that zinc, with its affinity for sulfur, oxidizes thiol groups and thereby inhibits the precursors of VSC. The aim of the study was to investigate whether, and to what extent, other metal ions with affinity for sulfur exert the same effect and whether a correlation exists between the sulfur affinity and VSC-inhibiting activity of these metals. VSC levels were measured on the 'morning breath' of 10 test subjects, using a portable sulfide monitor. The mouthrinses tested were aqueous solutions of zinc chloride, zinc citrate, stannous fluoride, cuprous gluconate, ferrous gluconate, and silver acetate, and they contained equimolar amounts of metals (1.47 mmol/I). The results showed that the ranking of Zn++ and Sn++ differed in the clinical test compared with sulfur affinity, and likewise with Ag+ and Fe++. It may therefore be concluded that there is no positive correlation between the inhibiting effect of metal ions on VSC and their affinity for sulfur.