SnF2 Solution Research Articles

A commercial SnF2 toothpaste formulation reduces simulated human plaque biofilm in a dynamic typodont model.

AimsWe present a dynamic typodont biofilm model (DTBM) incorporating (1) human dentition anatomy, (2) fluid flow over intermittently fluid bathed tooth surfaces and (3) an oxic headspace to allow aerobic and anaerobic niches to develop naturally, as a screening tool to assess the effect of stannous fluoride (SnF2) toothpaste against a simulated human plaque biofilm (SPB).Methods and resultsFirst, hydroxyapatite (HA) coupons were inoculated with human saliva/plaque and cultured at 37°C under air. Selected species representative of common commensal and anaerobic pathogens were quantified for relative abundance changes over 4 days by PCR densitometry to confirm the culture conditions allowed the proliferation of these species. A continuous culture DTBM reactor on a rocker table was inoculated with saliva/plaque and incubated at 37°C for 24 h. Tooth shear stress was estimated by particle tracking. A SnF2 toothpaste solution, or a sham rise was administered twice daily for 3 days to mimic routine oral hygiene. SPB biomass was assessed by total bacterial DNA and methylene blue (MB) staining. Early colonizer aerobes and late colonizer anaerobes species were detected in the HA and DTBM, and the trends in changing abundance were consistent with those seen clinically.ConclusionsTreatment with the SnF2 solution showed significant reductions of 53.05% and 54.4% in the SPB by MB staining and DNA, respectively. Significance and impact of study: The model has potential for assessing dentition anatomy and fluid flow on the efficacy of antimicrobial efficacy against localized SPB and may be amenable to the plaque index clinical evaluation.

Self-doped SnO2:F synthesis by aerosol-spray deposition technique and their application in relative humidity sensor devices

Fluorine-doped tin-oxide (SnO2:F) thin films were prepared by aerosol-spray deposition technique on soda lime glass substrate by one-step deposition process. Tin (II) fluoride (SnF2) was used as source of tin (Sn) and doping element fluorine (F), to synthesis a self-doped transparent conducting electrode. The doping concentration of the thin films was controlled by varying deposition temperature and the molar concentration of the SnF2 solution. Electrical resistivity of the samples was measured by Van Der Pauw method and the mobility was calculated by Hall measurement technique. SnO2:F thin films grown under optimum condition showed 1.2 × 10−4 Ω-cm resistivity and 6.5 × 1020/cm3 carrier concentration. Surface-free energy of the deposited thin films was calculated from the measurement of contact angle for three different probe liquids using the Wendt theory. Sample grown at optimum condition showed the lowest surface-free energy of 63.55 mJ/m2 with dominating polar component. Reduced graphene oxide was used to produce a resistive humidity-sensing device to study the effectiveness of FTO thin film as back electrode. Maximum of 18.27% responsivity was observed for the relative humidity of 90% along with the sensitivity of 1.16 Ω/% RH.

Preparation and Performance Evaluation of Pt/SnO2/KB As Cathode Catalyst of PEMFC

Several technical issues must be addressed to allow widespread commercialization of proton exchange membrane fuel cells (PEMFCs). In particular, the electrode catalyst that has high durability and an acceptable low cost (reducing Pt amount) is required. For this purpose, we prepared novel electrode supports which are modified Ketjen black with tin dioxide nanoparticles (SnO2/KB) and reported oxygen reduction reaction (ORR) activity as well as the durability of the resultant catalyst (after Pt loading) [1]. In particular, the ORR activity and the durability were strongly depended on the loading amounts of SnO2 as well as the heat treatment temperature [1]. In this presentation, the relation between the preparation condition of SnO2 / KB and the catalytic performance of the resultant catalyst are reported. The preparation detail of SnO2/KB can be found in our previous reports [1]. In brief, KB (Ketjen Black EC-300j) was dispersed in 0.01 mol dm-3 SnF2 aqueous solution for 24 h or 72 h. It was then dispersed in 0.01 mol dm-3 H3BO3 aqueous solution for 24 h. Subsequent heat treatment was carried out at 500 oC under Ar atmosphere. Loading of Pt nanoparticles on SnO2/KB was carried out by an impregnation method following drying under N2 atmosphere at 120 oC [1]. The catalysts were characterized by XRD, TGA under air, N2 adsorption and desorption measurements, FE-SEM observation, ICP measurements and CO pulse tests. The prepared catalysts were dispersed ultrasonically in 2-propanol and were dropped on a glassy carbon disk. A thin Nafion film with a calculated thickness of 80 nm was then formed. A glass half-cell equipped with an RHE (reversible hydrogen electrode) and a Pt mesh counter electrode was used in this study. 0.1 mol dm-3 HClO4 aqueous solution was used as the electrolyte. ORR activity was evaluated by Koutecky-Levich plot analysis based on the rotating disk electrode measurements under O2 atmosphere. The potential pulse durability tests were conducted between 1.0 V and 0.6 V at 60 oC. Electrochemical surface area (ECA) of Pt was estimated by cyclic voltammetry. From the TGA results, the weight ratios of SnO2 of SnO2/KB were 39wt% after 24 h in SnF2 solution and 35wt% after 2 h, respectively. Then, we hereafter called the catalyst prepared by 24 h-dispersing in SnF2 solution as Pt/39-SnO2/KB-24 and another as Pt/35-SnO2/KB-72. In FE-SEM images of Pt/39-SnO2/KB-24 and Pt/35-SnO2/KB-72, SnO2 particles of ca. 10 nm in the diameter were found on the surface of KB. On the other hand, Pt particle size could be estimated as 2 - 3 nm, which corresponding to the results of CO pulse tests. In addition, the particle size is estimated as 1.8 nm for Pt/KB. Table 1 shows the Pt particle size, the values of specific and mass activity for ORR and the ECA remaining after the durability test. The ORR activity is clearly increased by using SnO2/KB as the support; especially, the mass activity was high although the Pt particle size was large. Furthermore, the ORR activity is likely to be improved by increasing the time for dispersing in SnF2 aqueous solution. The durability is also improved by using SnO2/KB as the support. Then, we attempted to investigate the reasons for higher durability of the catalysts using SnO2/KB based on the degradation mechanisms. The stability of the supports (SnO2/KB) was elucidated the increasing rate of pseudo-capacitance during the potential pulse durability tests. The increasing rates of KB and Pt/35-SnO2/KB-72 were 12.5% and 8.5%, respectively, which shows that the durability of Pt/35-SnO2/KB-72 is higher than that of KB. In addition, to elucidate chemical stability of Pt, the stability tests were also conducted in O2 saturated HClO4 aqueous solution at 60 oC for 72 h. As the results, the dissolution ratio of Pt/35-SnO2/KB-72 was ca. 0.8%, which was almost half for the catalyst without SnO2. The migration of Pt particles was also one degradation factor. Then, we carried out identical location FE-SEM observation of the catalysts before and after heating at 300 oC under Ar atmosphere for 12 h [2]. The frequency for migration of Pt particles was found to be ca. 58% for Pt/KB. On the other hand, that of Pt/35-SnO2/KB-72 was 42%, which suggests that migration of Pt particles were depressed by using SnO2/KB as the support. [1] T. Kinumoto, et al, ECS Trans., 64(3), 199 (2014), 58(1), 1259 (2013), 50(2), 1701 (2012) and Electrochemistry, 79, 334 (2011). [2] T. Kinumoto, et al., Electrochemistry, 83(1), 12 (2015). Figure 1

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.

The first barium tin(II) bromide fluoride

In an effort to prepare barium tin(II) bromide fluorides for the first time, possibly similar to the chloride fluorides obtained earlier in our laboratory, precipitation reactions were carried out by mixing aqueous solutions of SnF2 and of BaBr2.2H2O. In contrast with the chloride fluoride system, a single powdered phase was obtained throughout the SnF2 – BaBr2 system, with the yield being maximum at X ≈ 0.25, where X is the molar fraction of barium bromide in the reaction mixture. Phase identification with the JCPDS database failed to produce a match, confirming that a new phase had been produced. The exact chemical composition of the new compound has not been obtained yet. Based on the X value for the maximum yield, the Sn/Ba ratio is likely to be 3/1 or 2/1. The Mossbauer spectrum at ambient conditions shows that bonding to tin(II) is covalent, therefore with the tin lone pair being stereoactive. The Mossbauer parameters (δ = 3.68 mm/s, Δ = 0.99 mm/s) are similar to those of SnBrF and of Sn2BrF5, thereby showing that tin is bonded to both fluorine and bromine. The larger isomer shift and lower quadrupole splitting than in tin(II) fluorides show that the stereoactivity of the tin lone pair is lower than in the fluorides. The Mossbauer parameters fit well the linear correlation of the quadrupole splitting versus the isomer shift” that has been shown to be present in other series of tin(II) compounds. The linear decrease on this correlation shows that the contribution of non-spherical orbitals (p and d) to the lone pair is a much larger contributor to the quadrupole splitting than lattice distortions. The structure is likely made of Ba2+ cations and tin(II) fluoride bromide polyatomic anions, with covalent bonding withinthe anions.

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

To compare the ability of two active ingredients - sodium fluoride (NaF) and stannous fluoride (SnF2 ) - to inhibit hydroxyapatite (HAP) dissolution in buffered acidic media. 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. 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). 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.

The protective effect of SnF2 containing toothpastes and solution on enamel surfaces subjected to erosion and abrasion in situ

Stannous fluoride solutions have shown promising protective effect against erosion/abrasion, but the effect of SnF2 toothpastes is uncertain. The aim of the study was to test the inhibiting effect of two SnF2 toothpastes and a SnF2 solution against erosive/abrasive wear in a single-blind, randomised in situ study, using a white light interferometer. Sixteen human molars were each divided into four specimens, mounted on mouth appliances and worn by 8 volunteers for 9 days. Specimens were brushed with toothpaste twice each day for 30 s either with fluoride-free toothpaste or toothpastes including SnF2. Toothpaste was left on the surface for 90 additional seconds. Group 1, fluoride-free toothpaste; Group 2, toothpaste A (0.4% SnF2, Solidox); Group 3, toothpaste B (0.454 % SnF2, Oral-B(®)); Group 4, brushed with fluoride-free toothpaste (30 s) and treated for 2 min with a 0.4 % SnF2 solution (1,000 ppm F). To mimic gastric reflux/vomit, specimens were etched for 2 min twice a day (0.01 M HCl). Procedures were performed extra-orally. The mean enamel wear (in μm) for the control specimens was: -29.2 ± SD 10.5; for group 2 -14.5 SD ± 9.3; for group 3 -33.3 SD ± 7.4, and for group 4 +0.4 SD ± 1.3. The specimens treated with SnF2 solution and toothpaste A showed significantly lower enamel wear than the control group. Toothpaste B gave no significant reduction in enamel wear. The SnF2 solution fully protected the enamel surface against erosive and abrasive challenges. The SnF2 toothpaste A (Solidox) showed less, but significant protection of the enamel, while no statistically significant protection was demonstrated by SnF2 toothpaste B (Oral-B(®) Pro-Expert).

The erosion-inhibiting effect of TiF4, SnF2, and NaF solutions on pellicle-covered enamel in vitro

Objective. The aim of this study was to compare the protective effect of TiF4, SnF2, and NaF treatment on the development of erosion-like lesions in pellicle-covered human enamel. Material and Methods. Twelve human molars were each divided into 5 specimens, 4 of which were immersed in saliva for 2 h. Three pellicle-covered specimens from each tooth were treated with a TiF4, SnF2, or NaF solution (all 0.5 M F) for 2 min. Control specimens, one with and one without pellicle, were included. Immersion in acid (0.01 M HCl) was carried out stepwise (2+2+2+2 min). The etching depths (in µm) were measured using white light interferometry. Results. Compared with the control with pellicle, TiF4 reduced enamel loss by 100% after 2 min and by 24% after 8 min of acid exposure. The corresponding values for SnF2 were 45% and 14%. NaF provided no significant protection of the surface. The pellicle-covered specimens showed reduced lesion depths after 6 and 8 min compared to the controls without pellicle. Conclusions. TiF4 gave the best protection against acid attack. SnF2 provided significant protection only after 2 min of acid exposure, while NaF had no significant protective effect.

Crystal structure and Mössbauer spectroscopic study of FeSnF6·6H2O

Large single crystals of FeSnF6·6H2O were grown when aqueous hydrofluoric solutions of SnF2 and FeF2 were allowed to evaporate in air. Tin-119 Mossbauer spectroscopy at ambient temperature shows a single line at slightly negative isomer shift relative to CaSnO3 at room temperature (δ=−0.380(6) mm/s, Δ=0). This is characteristic of tetravalent tin octahedrally coordinated by fluorine. The X-ray crystal structure shows that tin(IV) is coordinated by 6 fluorine atoms, and Fe(II) by 6 water molecules. Both sites show a slight distortion from octahedral symmetry: the six distances are equal (Sn-Fe=1.941(3) A and Fe-O=2.112(3) A), whereas there are two values of angles (Fe-Sn-F=90.4(1)° and 89.6(1)°; O-Fe-O=91.1(1)° and 88.9(1)°). The material is an ionic compound [SnF6]2−[Fe(H2O)6]2+.

Oxidation of divalent tin in aqueous solutions of SnF2 and 3D transition metals allowed to crystallize slowly in air

Chlorides, nitrates and sulfates of M (M=Mn, Fe, Co, Ni and Zn) were dissolved in aqueous solutions of SnF2 at M/Sn molar ratios of 0.5 to 3. No HF was used. The solutions were allowed to evaporate in air. Very small amounts of hexagonally shaped crystals of unknown materials were obtained for M=Mn, Co, Ni and Zn. Fe did not yield this phase. X-ray powder diffraction gives identical patterns for the four materials, which are therefore most likely isostructural, and showed that the products are not MSn2F6·6H2O or MSnF6·6H2O. Tin-119 Mossbauer spectroscopy gives a single line at negative isomer shift, characteristic of [Sn(IV)F6]2− ions.

Effect of stannous fluoride and tetracycline on periodontal repair after delayed tooth replantation in dogs.

Previous studies have indicated that inflammatory resorption and ankylosis, which are frequent sequela after delayed tooth replantation, can be greatly reduced by treating the root surface with 1% solutions of stannous fluoride and tetracycline. However, the SnF2 conditioning leaves a long-standing inflammatory reaction in the periodontal ligament. To examine whether a more dilute SnF2 solution would reduce postoperative inflammation without jeopardizing any beneficial effects, anterior teeth in three young adult beagles were extracted and allowed to air-dry for 45 min. They were then immersed in 0.1% SnF2 for 5 min, rinsed in saline, immersed in 1% doxycycline HCl for 5 min, rinsed, and replanted. Control teeth were air-dried and replanted without further treatment. Block biopsies were harvested after 4 wk of healing and processed for histometric analysis. In experimental teeth, 85% of the root surface area showed normal healing, compared to 33% in control teeth. Conversely, resorption and ankylosis were more frequent in controls than in experimental teeth. A persisting inflammatory reaction either adjacent to or at a distance from the root surface was seen in limited areas in both experimental and control teeth. Compared to preceding studies, the findings indicate that reducing the strength of the SnF2 solution from 1% to 0.1% may result in less persistent inflammation, at the cost, however, of less complete prevention of inflammatory resorption and ankylosis.

Root surface reactions to TiF4and SnF2solutions in vitro: An ultrastructural study

Previous studies have indicated that TiF4 and SnF2 differ in their demineralizing effect when applied topically to root surfaces at the same acidity. The aim of this study was to examine in more detail the outermost layer of root surface specimens by transmission electron microscopy (TEM) after short-term exposure to these acidic fluoride solutions. Root surface specimens were exposed for 1 min and 4 min to equimolar (1.1 M F) solutions of a) TiF4, native pH 1.0; b) SnF2, acidified to pH 1.0; and c) SnF2, native pH 2.5. The specimens were then rinsed in saline and processed for TEM. Exposure to TiF4 resulted in a partly demineralized zone 8-10 microns deep after 1 min and 5-27 microns deep after 4 min of application. A 0.1-micron-thick, electron-dense coating was present in all TiF4-treated specimens. Acidified SnF2 resulted in a completely demineralized zone, 4-7 microns deep, when applied for 1 min and 4 min, whereas SnF2 at native pH produced a 0.5- to 1.0-micron-wide partially demineralized zone. Unevenly distributed crystalline deposits were a frequent finding on SnF2-treated surfaces. The results indicate that solutions of TiF4 and SnF2 at native pH will cause only slight demineralization when applied topically to root surfaces.

Effect of TiF4solutions on bacterial growth in vitro and on tooth surfaces

The purpose of this study was to assess the antimicrobial effect of TiF4 as compared with equimolar solutions of NaF, APF, and SnF2 and to evaluate the effect, if any, on bacterial growth on topically treated tooth surfaces. In an in vitro study, paper discs impregnated with 20 microliters of equimolar solutions of SnF2, NaF, APF, and TiF4 were placed on blood agar plates seeded with Streptococcus mutans and Bacteroides gingivalis. Sterile saline was used as control. Similar growth inhibition zones were found for all fluorides. In the second part of the study six volunteers carried intraoral appliances containing enamel and root surface specimens treated with 1% TiF4 and untreated specimens for 18 h. Scanning electron microscopic examination of the experimental tooth surfaces showed great variation in bacterial growth between subjects, but no systematic difference between fluoride-treated and untreated specimens. Bacteria from test and control specimens were grown under aerobic and anaerobic conditions on blood agar and on mitis salivarius agar. Colony-forming unit counts showed great interindividual variations, but no differences could be observed between treated and untreated enamel or root surfaces. Thus, the hypothesis that the presence of a Ti-rich coating may influence bacterial colonization on TiF4-treated tooth surfaces could not be substantiated.

Effect of topical F- solutions on caries-like lesions in root surfaces.

Topical F- solutions, NaF, SnF2, TiF4, or Fe-Al-NaF, were applied to root surfaces to examine the effect on caries-like lesions produced in vitro. Extracted premolars were treated with a solution for 10 min prior to a 20-day period in acid gel. The lesions were studied by microradiography and light microscopy, and concentration profiles of 12 elements were determined by secondary ion mass spectrometry. The results indicated that the solutions retarded the development of lesions. The greatest effect was obtained with TiF4 and SnF2 solutions. Element analyses revealed that high concentrations of F (up to 3.5%) accumulated in the outer third of the lesion and that SnF2 and TiF4 formed depots in the cementum, although both Sn and Ti also penetrated the lesion. NaF had a weaker effect on lesion formation, but induced a high F concentration in the demineralized zones. The Fe-Al-F solution affected the lesion only marginally and deposited a relatively low F concentration in the lesion, although Fe and Al penetration and depot formation were noted.

Long‐term retention of TiF4 and SnF2 after topical application to dentin in dogs

As part of an evaluation of the potential of topical application of TiF4 in the prevention or arrest of root caries, the longevity of the titanium-rich glaze and the long-term retention of titanium and fluoride in exposed dentin surfaces were examined in dogs. For comparison, the effect of fluoride in combination with another cation, tin, was studied as well. Facets of exposed dentin were prepared in two beagles and treated for 1 or 4 min with either a TiF4 or an SnF2 solution (1.1 M F, native pH). After 3, 7, or 21 wk, the experimental surfaces were analyzed for fluoride, titanium, tin, and calcium using an electron microprobe. Dentin surfaces treated with TiF4 for 1 min showed fluoride concentrations ranging from less than 0.15% to 1.03%, while those treated for 4 min with SnF2 showed values from 0.22% to 1.28%. The calcium analyses revealed partial surface demineralization in one half of the SnF2-treated specimens, while this was a rare finding in the TiF4 group. The findings show that a brief application of TiF4 to exposed dentin results in approximately the same increase in fluoride content as a 4-min application of SnF2, with, however, less surface demineralization. In addition, the presence of a surface glaze may impart an added benefit to the use of TiF4 as a topical agent in the prevention of root caries.

Treatment of dentin with stannous fluoride – SEM and electron microprobe study

The effect of SnF2-treatment of dentin surfaces was investigated by means of scanning electron microscopy (SEM) and electron microprobe analysis. Human dentin was treated with aqueous SnF2 solutions of concentrations varying from 1 to 10%. The treatment periods lasted for 1, 5, 10, or 60 min. Both tin and fluoride were identified on the surfaces. The concentration varied depending on the extensiveness of the treatment. Immersion in 1 M KOH for 15 h removed both tin and fluoride from the surfaces. This reaction was not observed after immersion in H2O for the same time period. Examination of the SnF2-treated dentin surfaces showed a dense layer of globular particles and in addition some larger particles. The dentinal tubules were totally covered even after the treatment with the lowest concentration of SnF2. Deposition of tin- and fluoride-containing globules on dentin surfaces may be of clinical interest. This layer may have importance both for the caries resistance of dentin and for hypersensitivity reactions.

Plasma fluoride levels in man following intake of SnF2 in solution or toothpaste.

The degree and rate of fluoride absorption in five volunteers were studied after ingestion of SnF2 and NaF solutions or SnF2 toothpaste. The fluoride concentration in plasma was followed for eight hours. The relative bio-availability of fluoride was calculated and was similar for both the NaF and SnF2 solutions, although the latter solution showed a somewhat faster absorption rate. The bio-availability of fluoride from the SnF2 dentifrice was 85%.

Effect of daily rinsing with stannous fluoride on plaque and gingivitis: final report.

Two groups of children, ages 12 to 15, rinsed daily for 28 mo with aqueous fluoride solutions, one group using 0.05% sodium fluoride (NaF) and the other group using 0.1% stannous fluoride (SnF2). The SnF2 group had less plaque accumulation after four mo, but no difference was apparent at 16 and 28 mo. Gingivitis was less severe in the SnF2 group throughout the study, although the difference did not reach statistical significance. The 0.1% SnF2 solution, used daily as a mouthrinse, inhibits plaque formation, although this inhibitory effect is not apparent after 16 mo of rinsing.

Effect on plaque formation and acidogenicity of stored aqueous solutions of stannous fluoride.

Abstract – Stored aqueous solutions of SnF2 showed a reduced effect on plaque acidogenicity after 24 weeks, this being paralleled by reduced concentrations of Sn2+ and lowered pH. The plaque inhibiting effect was, however, maintained unchanged, indicating a different mechanism for this activity. Stored solutions caused a yellow dental stain probably consisting of SnS2.

セラミックス上の無電解ニッケルめっき

An electroless nickel plating on ceramics have been studied using α-Al2O3 and piezo-electric ceramics. Etching and catalizing steps indicated important role to obtain good adhesion. Etching with hot HCl followed by sensitising with SnF2 showed highest adhesion (>120kg/cm) on the piezoelectric ceramics. Ion micro analysis and SEM photomicrographs revealed that SnF2 solution may contribute to etching and sensitising the ceramics. Conventional etching treatments had no measurable effect on adhesion of α-Al2O3 ceramics. However, sensitising with SnF2 followed by two successive activation showed good adhesion. Furthermore, adhesion was increased after heat treatment. This metallization also provided reliable electric properties.