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PubMed1996

Autoimmune reactions in patients with silicone breast implants.

Silicone breast implants have been surgical routine for over 30 years. An association between silicone augmentation and immune related diseases has been reported in approximately 100 cases. In a retrospective single center study we investigated 36 non-selected women with silicone breast implants and 36 sex- and age-matched controls. Autoimmune reactions were evaluated by measuring antinuclear antibodies (ANA), rheumatoid factor (RF) and thyroid gland antibodies (TMS), along with angiotensin-converting enzyme (ACE), C-reactive protein (CRP) and other immunological and laboratory parameters. In the controls only 3 (8%) women had an elevated ANA titer and 1 demonstrated thyroid autoantibodies (microsomal), giving a total of 4 (11%) women with detectable autoantibodies. By contrast, 12 (33%) of the 36 women with silicone augmentation had raised ANA titers (> or = 1 : 80), a significantly higher percentage than in the control group (p < 0.02). Of the 12 women, 1 showed antismooth muscle antibodies (ASMA; titer 1 : 40) and 2 of the patients displayed antineutrophilic cytoplasm antibodies (ANCA; 1 : 320 and 1 : 40, respectively), one of the latter also being positive for rheumatoid factor. 2 further women demonstrated thyroid autoantibodies (microsomal), giving a total of 14 (39%) women in whom significant autoantibodies were detectable. Clinical symptoms (musculoskeletal) were present in 1 patient. Most of the observed autoantibodies were organ-unspecific, with a predominance of elevated ANA titers of the heterogeneous type and not related to a distinct clinical entity. However, none of the investigated women with silicone breast implants showed clinical symptoms or signs of connective tissue disease according to ARA criteria.

Acute-Phase Proteins↗
PubMed1998

The results of treatment of synovitis of the wrist induced by particles of silicone debris.

Synovitis of the wrist induced by particles of silicone debris is a destructive inflammatory process. Many silicone-rubber carpal implants remain in place, and there are few reports regarding the treatment of this condition. The purpose of the present study was to examine the results of treatment of synovitis induced by particles of silicone debris. Twenty-eight patients were identified, with use of computerized indexing, as having been evaluated for silicone-induced synovitis between 1972 and 1992. Seventeen of the twenty-eight patients were included in the study. At the time of the latest follow-up, twelve of the seventeen patients had pain, thirteen of the fourteen patients for whom radiographs were available had evidence of osteolysis typical of that associated with debris-induced synovitis, and eight of the seventeen patients reported difficulty with activities of daily living because of problems with the wrist. Seven patients had been treated non-operatively, and ten had been treated operatively. With the small number of patients available for study, we could not detect a significant difference between the two groups with respect to pain, perceived limitation of motion, difficulty with activities of daily living, grip strength, or the total range of motion of the wrist. There was no significant difference between the two groups with regard to the age at the time of the initial procedure, the time to the diagnosis of the synovitis, and the duration of follow-up after treatment. There was no clear advantage to removal of the implant and débridement with or without arthrodesis of the wrist or other reconstructive procedures. We recommend caution when a reconstructive or salvage procedure in the wrist is selected for a patient who has synovitis induced by particles of silicone debris.

Adult↗
PubMedDate not supplied

Silicone absorption of elastomeric closures--an accelerated study.

There is a trend in the parenteral industry to move from the use of elastomeric closures which are washed, siliconized, dried and sterilized in-house at the pharmaceutical manufacturers' site to pre-prepared closures purchased from the closure supplier. This preparation can consist of washing to reduce particle-load and bioburden, siliconization, placement in ready-to-sterilize bags and may eventually extend to sterilization by steam autoclave or gamma irradiation. Since silicone oil lubrication is critical to the processability/machinability of closures, research was designed to investigate this phenomenon in closures prepared using the Westar RS (Ready-to-Sterilize) process. This paper presents the data gathered in a study of the characteristic of silicone absorption into elastomeric closures under accelerated conditions. Variables such as silicone viscosity, rubber formulation, effect of sterilization and others are considered.

Absorption↗
PubMed1996

[Pathological examination of 10 eyes with silicone oil injection].

OBJECTIVE: To find the histopathologic findings about 10 eyes of 10 patients with silicone oil injection. METHODS: The operative procedures included retinal detachment surgery, pars plana vitrectomy and silicone oil injection. The globes were enucleated 4 to 27 months after silicone oil injection. Paraffin sections were made for light microscopic examination. RESULTS: The retina showed severe degeneration, pre- and sub-retinal membranous fibrous tissue proliferation. The round empty vacuoles formed by silicone oil could be seen in the proliferative membrane. CONCLUSIONS: It is demonstrated that silicone oil has great toxic effect to the detached retina and it may stimulate the development of proliferative vitreoretinopathy.

Adolescent↗
PubMed1998

Fine-bore cannulas for peripheral intravenous nutrition: polyurethane or silicone?

The peripheral intravenous route is being used more frequently for the administration of short- to medium-term parenteral nutritional support. Dedicated fine bore cannulas have significantly reduced the incidence of thrombophlebitis. Currently available cannulas are made of polyurethane or silicone. We present our experience with a 23G silicone cannula and a 22G polyurethane alternative. Fifty-four silicone cannulas were used with a median survival of only 3 days, compared with 7 days for 90 polyurethane cannulas (P < 0.0001). Only 22% of silicone cannulas were removed electively compared with 56% of polyurethane cannulas (P < 0.00005). The most common cause for silicone cannula removal was occlusion (48%), which occurred in only 8% of polyurethane cannulas (P < 0.00001). Polyurethane cannulas develop fewer complications and are more effective in the delivery of peripheral intravenous nutritional support.

Adult↗
PubMed1998

Silicone breast implants: an oncologic perspective.

In 1992, the FDA decided that silicone gel-filled breast implants would be available only through controlled clinical studies, despite the fact that they had been used for mammoplasty in millions of women around the world for more than 30 years. The safety of silicone breast implants had been called into question after several reports of a possible association between the implants and the subsequent development of connective tissue diseases. Such reports led to general public concern fueled by popular media attention and multiple class-action lawsuits against the product's manufacturers. It was in this climate that the FDA was forced to make its decision. This article reviews current scientific evidence on the safety of silicone gel-filled breast implants. Issues pertinent to oncology are highlighted. These include the possible carcinogenic effect of silicone gel, the safety of irradiating breasts with silicone implants, and the ability to mammographically image the implanted breast.

Breast Implants↗
PubMed1998

[Ultrasonic diagnosis of retinal detachment after internal tamponade with silicone oil].

The authors evaluate the results of ultrasound examination of 20 patients with retinal detachment (20 eyes) after pars plana vitrectomy with silicone oil tamponade. Ultrasound diagnostic method is necessary in cases with non-transparent optic media. Silicone oil in the space of vitreous cavity has a character of a swimming water-drop and his physical properties can change the echography results. Between the eye-wall and silicone oil is a virtual space, which could be well visualised by ultrasound. The patients are divided into 2 groups. In the 1st group there were 7 eyes with transparent optic media and retina was detached under the silicone oil. By ultrasound the retina detachment echo was localised between the echos of silicone oil and eye wall. In the 2nd group there were 13 eyes with non-transparent optic media. In 6 cases (41.6%) the retinal detachment echo was visualised. The retinal detachment was confirmed by vitreo-retinal surgery.

Adult↗
PubMed1998

Temporary wound covering with a silicon sheet for the soft tissue defect following open fasciotomy. Technical note.

OBJECTIVE: Temporary covering of a defect of the soft tissues with a silicon sheet after fasciotomy in the treatment of compartment syndrome. DESIGN: Retrospective study. SETTING: University Hospital, Tübingen. PATIENTS: From January 1991 to June 1996, open fasciotomy was performed a total of 18 times on 17 patients with compartment syndrome. In 17 of the 18 cases acute vascular ischemia was the cause of the compartment syndrome. INTERVENTIONS: For the 18 necessary fasciotomies, a silicon sheet was temporarily used to cover the defect of the soft tissue temporarily a total of 9 times. The silicon sheet was gradually drawn together and the wound was finally closed with a secondary suture. RESULTS: In 6 of the 9 cases a secondary suture could be performed without any difficulties after the swelling had subsided, and a meshgraft covering was not necessary. Only one patient suffered from wound infection because the silicon sheet had not been sutured correctly. In the other cases there was no sign of infection. The wound dressing was changed painlessly and furthermore, an improved cosmetic result was observed. CONCLUSIONS: There are considerable advantages in the use of a silicon sheet as a temporary covering for the defect of the soft tissues in the treatment of compartment syndrome: lower costs because of shorter hospitalisation and the dressing change is practically painless. A reduced risk of infection and improved cosmetic results are further advantages of this method.

Aged↗
PubMed1997

On reasons of 29Si NMR chemical shift/structure relations for silicon oxides, nitrides, and carbides: an individual-gauge-for-localized-orbitals study.

For alpha-quartz, monoclinic ZSM-5, alpha- and beta-Si3N4 and SiC-6H polytype, the silicon chemical shifts have been calculated using the IGLO (individual gauge for localized orbitals) method and models of different size in real crystal geometry. The result is a theoretical chemical shift scale, which is very similar to the corresponding experimental scale from 29Si MAS NMR experiments. It is shown that the assignment of isotropic silicon chemical shifts of crystallized solids based on theory is a method of practical applicability, also in cases where experimental methods or empirical relations fail. The two NMR spectral lines of alpha-Si3N4 are for the first time assigned to the crystallographic positions. The partition of the silicon chemical shifts into localized contributions from different parts of the model allows insight into the interactions around the resonance nucleus due to substituent and geometry variations leading to silicon chemical shifts.

Carbon Compounds, Inorganic↗
PubMedDate not supplied

[Exposure to silicon carbide fibers in the production of carborundum].

Recent reports have shown that not only silicon carbide dusts but also fibres are liberated into the working environment during the various phases of silicon carbide production (using Acheson furnaces), thus creating a further potential health hazard. An environmental hygiene survey was conducted in a silicon carbide production plant with the aim of quantifying airborne dusts and fibres. Although dust levels were below 50% of the TLV, high concentrations of fibres were observed (analyzed via optical microscopy using the criteria for asbestos fibres), which in some locations reached levels of 2000 fibres/litre with means (GM) between 100 and 780 fibres/litre according to department. These results are assessed in the light of the growing interest of researchers in the experimental effects of silicon carbide fibres.

Carbon↗
PubMed2002

Effects of antimony on the surface tension of molten silicon.

The effect of antimony concentration (C(Sb)/mass%) on the surface tension of molten silicon has been determined with the sessile drop method in the temperature range from 1693 to 1773 K and in the range of the oxygen partial pressure, Po(2), in an Ar atmosphere from 10(-23) to 10(-21) MPa. The results show that the surface tension of molten silicon decreases with increasing Sb concentration in the range of C(Sb)<0.9 mass%, which indicates positive adsorption of Sb in molten silicon and can be fairly described with the Szyszkowski's equation. The maximum decrease rate of surface tension is about 65 mN m(-1) (mass% C(Sb))(-1), and the temperature coefficient of surface tension, (partial differential sigma/ partial differential T)C(Sb), increases with increasing C(Sb). The evaporation of the systems was only observed between the melting points of antimony (904 K) and silicon (1683 K), and the surface tension presents no dependence on measuring time above the melting point of silicon.

Journal Article↗
PubMed2001

Analysis of high purity graphite and silicon carbide by direct solid sampling electrothermal atomic absorption spectrometry.

Solid sampling electrothermal atomic absorption spectrometry using the boat technique and a transversely heated graphite tube was applied to direct analysis of graphite and silicon carbide powders for 14 and 12 impurity elements, respectively. With graphite, for all analytes under investigation, a very effective in-situ analyte/matrix separation was achieved. That was the case also for analytes in silicon carbide requiring atomization temperatures below 2400 degrees C. At higher atomization temperatures, the decomposition products of silicon carbide give rise to significant background, which can still be corrected. Sample amounts of up to 4 mg graphite and 8 mg silicon carbide per analysis cycle were applied. For all analytes in both materials, limits of detection at the lower ng g(-1) and sub-ng g(-1) level were achieved, excluding arsenic for which they were 50 ng g(-1) and 23 ng g(-1) for graphite and silicon carbide, respectively. Quantification was performed using calibration curves measured with aqueous standard solutions. The accuracy was checked by comparison of the results with those obtained by instrumental neutron activation analysis and by other independent methods.

Journal Article↗
PubMed1988

Study of fatty acids in atheroma induced in rabbits by an atherogenic diet with or without silicon i.v. treatment.

Fifty-two rabbits were submitted for two months to an atherogenic diet with or without addition of silicon in the form of an I.V. silicon organic compound and compared to a control group of 21 rabbits. Out of the 26 rabbits receiving cholesterol alone, 23 showed atheromatous lesions; out of the 26 rabbits receiving cholesterol + silicon, only 8 had lesions. Free fatty acids, total fatty acids and esters were studied in the plasma and in the aorta. During atheroma, saturated fatty acids decrease, in particular 18:0, unsaturated fatty acids increase, in particular 18:1, 18:2, 20:4; with added silicon the variations are less important: in free fatty acids in plasma, there is a decrease of 20:4; in cholesterol esters in plasma and aorta an increase of 18:0 and a decrease of 18:2. There is a negative correlation between atheromatous lesions and myristic and stearic acids, and a positive correlation between oleic, linoleic and arachidonic acids and atheroma. Arachidonic acid, involved in phenomena of lipid peroxidation, decreased in the silicon treated rabbits.

Animals↗
PubMed2004

Effect of boron on the surface tension of molten silicon and its temperature coefficient.

The influence of boron concentration (C(B)/mass%) on the surface tension of molten silicon has been investigated with the sessile drop method under oxygen partial pressure P(O(2))=1.62x10(-25)-2.63x10(-22) MPa, and the results can be summarized as follows. The surface tension increases with C(B) in the range below 2.09 mass%, and the maximum increase rate of the surface tension is about 30 mN m(-1)(mass% C(B))(-1). The temperature coefficient of the surface tension, ( partial differential sigma/ partial differential T)C(B), was found to increase with the boron concentration in molten silicon. At the interface between molten silicon and the BN substrate, a discontinuous Si(3)N(4) layer was reckoned to form and the layer might prevent BN from dissolving into the molten silicon. Since dissolved boron from the BN substrate into the molten silicon is below 0.054 mass% and the associated increase in surface tension is below 1.5 mN m(-1), the contamination from the BN substrate on the surface tension can be ignored. The relation between the surface tension and C(B) indicates negative adsorption of boron and can be well described by combining the Gibbs adsorption isotherm with the Langmuir isotherm.

Journal Article↗
PubMed2001

Characterization and modeling of the metal diffusion from deep ultraviolet photoresist and silicon-based substrate.

The radioactive tracer technique was applied to investigate the out-diffusion of the transition metals (Cu, Fe and Co) from deep ultraviolet (DUV) photoresist into underlying substrate. Two important process parameters, viz., baking temperatures and substrate types (i.e., bare silicon, polysilicon, silicon oxide and silicon nitride), were evaluated. Results indicate that the out-diffusion of Co is insignificant, irrespective of the substrate type and baking temperature. The out-diffusion of Cu is significant for substrates of bare silicon and polysilicon but not for silicon oxide and nitride; for Fe, the story is reversed. The substrate type appears to strongly affect the diffusion, while the baking temperature does not. Also, the effect of solvent evaporation was found to play an important role in impurity diffusion. Using the method of numerical analysis, a diffusion profile was depicted in this work to describe the out-diffusion of metallic impurities from photoresist layer under various baking conditions. In addition, the effectiveness of various wet-cleaning recipes in removing metallic impurities such as Cu, Fe and Co was also studied using the radioactive tracer technique. Among the six cleaning solutions studied, SC2 and SPM are the most effective in impurity removal. An out-diffusion cleaning model was first proposed to describe the cleaning process. A new cleaning coefficient, h(T), was suggested to explain the cleaning effect. The cleaning model could explain the tracer results.

Journal Article↗
PubMed1999

IV-VI semiconductor growth on silicon substrates and new mid-infrared laser fabrication methods

This paper reviews results from research conducted at the University of Oklahoma on the development of new IV-VI semiconductor (lead salt) epitaxial growth and laser fabrication procedures that can ultimately lead to dramatic increases in mid-IR laser operating temperatures. Work has focused on growth of IV-VI semiconductor laser structures on silicon substrates using buffer layers that contain BaF2. Recent experiments show that it is possible to obtain high crystalline quality IV-VI semiconductor layer structures on (111)-oriented silicon substrates using molecular beam epitaxy (MBE) or on (100)-oriented silicon using a combination of MBE and liquid phase epitaxy (LPE). Experimental data for IV-VI semiconductor layer structures grown on silicon substrates including crystalline quality information as determined by high resolution X-ray diffraction (HRXRD) measurements and absorption edge information as determined by Fourier transform infrared (FTIR) transmission measurements are presented. Results show that these materials can be used to fabricate lasers that cover the 3 microns (3333 cm-1) to 16 microns (625 cm-1) spectral range. Removal of IV-VI semiconductor laser structures from the silicon growth substrate by dissolving BaF2 buffer layers with water is also demonstrated. This allows epitaxially-grown laser structures to be sandwiched between two heat sinks with a minimum of thermally resistive IV-VI semiconductor material. Theoretical modeling predicts that IV-VI lasers fabricated this way will have maximum continuous wave (cw) operating temperatures at least 60 degrees higher than those of IV-VI lasers fabricated on PbSe or PbTe substrates.

Journal Article↗
PubMed2000

Determination of main and minor components of silicon based materials by a combustion with elemental fluorine. Separation of gaseous fluorination products by carrier gas distillation and gas mass spectrometry

For the determination of main and minor components in silicon-based ceramic powders, a decomposition by a combustion with elemental fluorine and separation of the volatile fluorination products by a carrier-gas distillation with a subsequent detection by quadrupole mass spectrometry is described. The necessity and success of the separation step is demonstrated for the determination of boron as a minor constituent in SiC, where the spectral interferences of silicon on the boron signals are decreased considerably. The method developed is shown to be directly applicable to determination of silicon in Si3N4, SiC, and SiO2. The determination of nitrogen in Si3N4 requires additional effort, to separate nitrogen from the excess of fluorine. For the determination of boron, a complete mobilization of BF3 is assured by the presence of an adequate amount of GeF4. Analysis results obtained with different types of calibration show a precision of 30 microg for boron at the milligram-per-gram level and a precision between 0.5 and 2% (m/m) for the main components, silicon and nitrogen. Within these standard deviations, the results agree well with the values expected from the stoichiometry, with the results for silicon and boron obtained by wet chemical decomposition and slurry techniques in combination with ICP-OES and with the results for nitrogen obtained by carrier gas heat extraction.

Journal Article↗
PubMed2006

Novel silicon-containing polyurethanes from vegetable oils as renewable resources. Synthesis and properties.

Hydrosilylation of methyl 10-undecenoate (UDM) with phenyl tris(dimethylsiloxy)silane (PTDS) followed by a reduction of carboxylate groups was used to obtain a silicon-containing polyol with terminal primary hydroxyl groups (PSi194). Biobased silicon-containing polyurethanes, with a silicon content between 1.7% and 9.0%, were prepared from epoxidized methyl oleate-based polyether polyol (P184), PSi194, and 4,4'-methylenebis(phenyl isocyanate) (MDI). The thermal, mechanical, and flame-retardant properties of these materials were examined. The most notable change resulting from the incorporation of PSi194 is the appearance of melting endotherms of variable enthalpy and position and a downward shift in the T(g). The incorporation of silicon does not change the thermal stability but enhances the stability of the char under air atmosphere. Polyurethanes with higher silicon content no longer burn in ambient air without complementary oxygen, which suggests that these biobased materials are very interesting for applications that require fire resistance.

Organosilicon Compounds↗