Properties of test metal ceramic titanium alloys

Four test alloys were prepared using a high frequency centrifugal casting machine and a ceramic crucible for the development of titanium bonding alloys that can be cast in the ordinary atmosphere. Of these alloys, 10.06% Ti, 78.79% Ni, 9.02% Pd, 1.77% Sn and 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir could be cast by the conventional high frequency centrifugal method; however, 89.18% Ti, 8.75% Ni, 1.03% Pd, 0.28% Sn and 89.81% Ti, 8.15% Ni, 1.01% Pd, 0.18% Sn, 0.67% Ir could be cast only by the argon are melting method. The alloys 10.06% Ti, 78.95% Ni, 9.02% Pd, 1.77% Sn and 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir showed excellent physical and mechanical properties and bonding strengths, surpassing those of the commercial alloys TPW and Unimetal. Concerning the elution of component elements, the amounts of titanium eluted from these alloys were far smaller than those from pure titanium or a Ti-6Al-4V alloy, and nickel elution, which has become an issue in relation to metal allergy, was almost nil in contrast to Unimetal (Ni-Cr alloy). The alloy 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir showed properties that indicated its favorable use as an alloy for the bonding of dental porcelain.

Structure of bis(2-chloroethyl)ammonium hexachlorostannate

[(ClCH2CH2)2NH2]2SnCl6, M(r) = 617.48, monoclinic, C2/c, a = 15.67 (2), b = 13.54 (2), c = 13.24 (2) A, beta = 127.9 (2) degrees, V = 2217 A3, Z = 4, D chi = 1.85 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 23.70 cm-1, F(000) = 1208, T = 295 K, R = 0.058, wR = 0.071 for 1231 unique reflections. The structure consists of discrete (ClCH2CH2)2NH2+ cations and octahedral SnCl6(2-) anions with the Sn sitting on the twofold axis.

Evaluation of reduction-mediated labelling of antibodies with technetium-99m

Monoclonal antibodies can be labelled with technetium-99m by prereduction of the antibody with 2-mercaptoethanol, then reduction of pertechnetate with an aliquot of a stannous kit, resulting in greater than 97% labelling without the need for further purification. The present work shows that equally high labelling can be obtained with a variety of weak ligands and that the optimum quantity of stannous chloride is 2-4 micrograms. Although the label was stable to challenge with excess DTPA, cysteine was able to remove a portion of the label. We have also shown that this technique works with the IgG2a isotype in addition to the previously reported IgG1 isotype. This approach is simple, convenient and reproducible, and warrants further clinical evaluation.

ESCA study on dental alloy surfaces modified by Ga-Sn alloy

A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect. A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga2O3 and SnO2, less than 1-2nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.

A new method for promoting adhesion between precious metal alloys and dental adhesives

A new, simple method of modifying the adherend metal surface by a liquid Ga-Sn alloy (Adlloy) was applied to dental precious and base-metal alloys for adhesion with 4-META adhesive resin. Adhesions of 4-META resin to three other surface states--as-polished, oxidized at high temperature, and electroplated tin--were also performed for comparison with the adhesion on Adlloy-modified surfaces. Bond strength measurements were made, and the durability against water at the adhering interface was evaluated. The Adlloy-modified gold alloys (Type IV and 14 K) and silver-based alloys (Ag-Pd and Ag-Cu) showed not only high bond strengths but also excellent water durability at the adhesion interface. Surface modification by Adlloy, however, did not affect adhesion to Ag-In-Zn and base-metal (SUS, Co-Cr, and Ni-Cr) alloys. Adhesion to the tin-electroplated specimens was comparable with that to the Adlloy-modified specimens.

Effect of hygiene instrumentation on titanium abutments: a scanning electron microscopy study

Implant abutments can be exposed to a variety of oral prophylaxis procedures. In this in vitro study, titanium abutments were subjected to five oral prophylaxis treatment modalities; a metal scaler, a plastic scaler, a rubber cup, a rubber cup with tin oxide, and an air-powder abrasive. The abutment surfaces were then examined under both light and scanning electron microscopes. The metal scaler was seen to roughen the titanium surface. All other modalities tested appeared to smooth the titanium surface by removing surface debris and rounding off the sharp machined grooves present on the untreated abutment surface.

Evaluation of the 111In-(Sn)-citrate method to label antibodies for radioimmunotargeting studies

Monoclonal antibody against carcinoembryonic antigen (CEA) was labeled by the 111In-(Sn)-citrate technique and its characteristics were determined from the point of radioimmunotargeting studies. Antibodies of high specific radioactivity could be labeled with a high labeling yield of greater than 90% without any further purification step, and without loss of immunoreactivity. In biodistribution studies using nude mice bearing CEA-producing tumors, an extremely high tumor-to-blood ratio (40 on day 6) was obtained since 111In in the blood cleared very rapidly, but nonspecific 111In localized in the liver and spleen should be seriously considered.

Potential photosensitizers for photodynamic therapy. III. Photophysical properties of a lipophilic chlorin and its zinc and tin chelates

Photophysical properties of a lipophilic chlorin derivative and its zinc and tin chelates were investigated in chloroform. The quantum yields of the fluorescence phi F, of the S1----T1 intersystem crossing phi T and of singlet oxygen (1 delta g) formation phi delta, as well as the Stern-Volmer constants for the quenching of the S1 states by oxygen and the rate constants of quenching of O2(1 delta g) by the chlorins were measured. In comparison to the metal-free chlorin an increase of phi T and a decrease of phi F have been observed for the metal-containing derivatives, whereas the phi delta values remain constant.

Release of corrosion products from amalgam in phosphate containing solutions

The effect of phosphate concentration on corrosion was compared for two types of amalgam: a conventional alloy (ANA 68) and a high-Cu admixed alloy (Dispersalloy). The test specimens were stored for 4 months in electrolytes containing 85 mM NaCl and 85 mM NaCl with 2.5, 10, or 100 mM phosphate buffer respectively. The solutions were renewed each month and analyzed for Cu, Zn, Sn, Hg, and Ag in an atomic absorption spectrophotometer. The surfaces and cross-sections of the specimens were studied in a scanning electron microscope (SEM) with an energy dispersive detector (EDAX). The corrosion products, mainly Sn-compounds, at the surface of the amalgams were less in the solutions containing high concentrations of phosphate. In cross-section subsurface corrosion of the high-Cu amalgam was observed especially in specimens immersed in the NaCl solution without phosphate. The conventional amalgam showed surface corrosion only. The decrease in release of elements with time from the conventional amalgam in all the experimental solutions might indicate passivation. For the high-Cu amalgam the release of elements increased with time, except for Cu and Sn in the solution with 100 mM phosphate, indicating that phosphate inhibits corrosion of the Cu-Sn-phases. Release of corrosion products from the high-Cu amalgam was more dependent on the presence of phosphate than the conventional amalgam.

Tin oxide coating of aluminous porcelain by reactive ion plating

Alumina reinforced dental porcelain has been coated directly with tin oxide by reactive ion plating. Samples were prepared at different distances from the tin source in the ion plating rig. Tensile bond strengths of treated and untreated porcelain discs to a commercially available phosphate-methacrylate based dental cement were determined. Bond strengths of certain coated samples were found to be in excess of the cohesive strength of the porcelain substrates (greater than 7.8 MPa), whereas untreated porcelain achieved an average bond strength of only 3.4 MPa. The microstructures of coatings produced under conditions similar to those which yielded the maximum bond strength were examined in a scanning electron microscope and were found to be approximately 0.5 microns thick. It is believed that ion plating has great potential for rendering inert ceramic surfaces capable of direct bonding to dental cements.

Thermal effect on the dissolution of mercury from two dental amalgams

Various factors affect dissolution of mercury from dental amalgams. In this study we examined the effect of temperature on the release of mercury from two dental amalgams, namely an admixed high-copper amalgam (Contour) and a new tin- and copper-free amalgam (Composil). Ten cylindrically-shaped specimens of each type of amalgam were used in this investigation, and were divided into two equal groups. The five specimens in each group were each incubated in 10 ml purified water at either 37 degrees C or 60 degrees C, with a change of water every 24 h over an 8-day period. The quantity of mercury released from each amalgam specimen during each incubation period was expressed as micrograms cm-2 24 h-1. The amount of mercury released was estimated by cold-vapour atomic spectrometry. The results demonstrate that specimens incubated at 60 degrees C released significantly larger amounts of mercury than specimens incubated at 37 degrees C for both types of amalgam. The release of mercury by Composil was significantly greater than that by Contour (P less than or equal to 0.0001) for both temperatures studied. Raising the incubation temperature caused a disproportionate increase in mercury release from Composil compared to Contour.

Technetium-99m-labeled platelets: comparison of labeling with a new lipid-soluble Sn(II)-mercaptopyridine-N-oxide and 99mTc-HMPAO

Platelets pretinned with a neutral Sn(II)-2-mercaptopyridine-N-oxide (SN-MPO) were labeled with 99mTc and compared to those labeled with 99mTc-HMPAO. The conditions of labeling platelets, e.g. concentrations of platelets and Sn(II)-MPO, 99mTc in ACD-saline or ACD-plasma media, pH and incubation time, were optimized using canine platelets. Moderate labeling efficiency was obtained with 20 micrograms of tin(II) chloride and 30 min incubation with Sn-MPO and pertechnetate. The viability of labeled platelets was determined by platelet recovery and platelet survival times in Beagle dogs. The labeling efficiency with platelets from 43 mL of blood was 62.8 +/- 7.6%. The platelet recovery was 35.7 +/- 5.0% and exponential survival time was 34.6 +/- 3.1 h compared to 43.3 +2- 12.0% and 29.5 +/- 3.3 h for 99mTc-HMPAO-labeled platelets. These values were significantly (P less than 0.01) lower than 111In-labeled platelets. Biodistribution in dogs indicates lower retention in blood, spleen and liver after some initial 99mTc excretion in urine. The platelet deposition with 99mTc platelets (Sn-MPO method) on polyurethane angio-catheters was similar to 99mTc-HMPAO-labeled platelets. This study indicates that the platelets could be successfully labeled with pertechnetate in a cost-effective manner for the evaluation of thromboembolic complications.

The effect of tin on the corrosion behavior of the Ag-Hg phase of dental amalgam and dissolution of mercury

The anodic polarization behavior of the Ag-Hg matrix phase of dental amalgam (gamma 1) and the rate of mercury dissolution were examined as a function of the tin content. The objectives were to determine the effect of tin on the electrochemical behavior and dissolution of mercury and to provide evidence on whether tin dissolves in the gamma 1 phase or precipitates as a tin-rich phase. Anodic polarization curves were recorded for specimens of the gamma 1 phase containing 0-1.5% Sn and for the gamma 2 phase and a gamma 2-containing dental amalgam, in synthetic saliva. Mercury dissolved in synthetic saliva in 24 h was determined for the gamma 1 phase containing 0-1.0% Sn, with cold-vapor Atomic Absorption Spectrophotometry used for mercury analysis. Tin induced passive behavior of the gamma 1 phase and suppressed mercury dissolution. The passive gamma 1 phase did not exhibit a breakdown of passivity occurring at the gamma 2 phase. The results were consistent with the tin presence in gamma 1 in a solid solution, rather than in tin-rich precipitates, and indicated that at least 1.5% Sn can be dissolved in gamma 1 at 37 degrees C.

Copper-, indium-, tin-, and calcium-fluoride admixed amalgams: release rates and selected properties

A conventional (Minimax), two single-particle high-Cu (Summalloy and Aristaloy CR), and two dispersed-phase (Cluster and Phasealloy) amalgam alloys were each admixed with 0.5 wt% of CuF2, InF3, SnF2, and CaF2, and evaluated for F-, Cu, and Sn release, as well as for corrosion resistance, microstructure, and compressive strength. Over a 43-week interval, only Cluster revealed somewhat of a sustained F- release in artificial saliva. A ranking for F- release was Cluster (highest), Summalloy, Phasealloy, Minimax, and Aristaloy CR. The effectiveness of the F- compounds in releasing F- followed CuF2 (highest), SnF2, InF3 (1.0%), InF3, and CaF2. Amalgams with admixed CuF2 released both the most Cu and increased Sn. For three amalgams, CaF2 admixtures also increased the Cu release. Constant-potential coulometry distinguished among the different fluoride amalgams. Only Minimax revealed a significant reduction in compressive strength with two admixtures. Microstructural analysis revealed an increased pore distribution around the Ag-Cu dispersed particles, and it was assumed that the F- particles were contained within the pores, since SEM, EDS with a low element detector, and ESCA were all unable to detect the F- particles.

A sensitive electrochemical method for quantitative hydroperoxide determination

We report a general assay for hydroperoxides that is simple, selective, and sensitive. The assay is based on the reduction of hydroperoxides by glutathione (GSH) catalyzed by GSH peroxidase. Stoichiometric amounts of oxidized glutathione (GSSG) are produced that are separated from GSH by HPLC. GSSG eluting from the column is quantitated with a coulometric detector operating in the oxidizing mode (E = 0.82 V vs Pd). Picomole amounts of GSSG can be measured and related to the hydroperoxide concentration in the incubation mixture. GSH peroxidase has broad substrate specificity to many different hydroperoxides. Therefore, this method allows the determination of the total hydroperoxide concentration in the reaction mixture. For analysis of peroxidized phospholipids, phospholipase A2 is included in the reaction to release fatty acid hydroperoxides from the 2-position of the glycerol moiety. The presence of hydroperoxide is verified by addition of sodium borohydride or stannous chloride to sample extracts of biological fluids before analysis. The applicability of this method was tested by examination of human plasma from normal individuals for hydroperoxide levels.