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PubMed2003

Structure-property relationships of silicone biofouling-release coatings: effect of silicone network architecture on pseudobarnacle attachment strengths.

Model silicone foul-release coatings with controlled molecular architecture were evaluated to determine the effect of compositional variables such as filler loading and crosslink density on pseudobarnacle attachment strength. Pseudobarnacle adhesion values correlated with filler loadings in both condensation and hydrosilylation-cured silicones. Variation of crosslink density of hydrosilylation-cured silicones had an insignificant effect on attachment strength. X-ray photoelectron spectroscopy (XPS) indicated that the mode of failure upon detachment of the pseudobarnacle was dependent upon the crosslink density; samples with high crosslink density failed cohesively within the silicone.

Adhesiveness↗
PubMed1994

Silicone migration to the pleural space associated with silicone-gel augmentation mammaplasty.

We present a case report of silicone particles found in the pleural fluid of a patient 20 years after bilateral augmentation mammaplasty with silicone-gel implants. The patient's history is notable for bilateral replacements of implants and multiple closed capsulotomies several years subsequent to the original augmentation procedure. A ruptured left implant was found in 1991 when she first experienced pain in the upper back. A left pleural effusion developed subsequently. Analysis of the pleural effusion fluid by scanning electron microscopy suggested the presence of silicone. All laboratory results were normal, and the effusion did not recur after thoracentesis. The patient has been under close follow-up, and further pulmonary complications or other symptoms have not developed. This case report demonstrates the potential for silicone migration to the pleura and the possibility of subsequent pulmonary complications, such as pleural effusion.

Female↗
PubMed2002

Silicone migration from silicone-injected breasts: magnetic resonance images.

Injection of liquid silicone into the breast was performed illicitly in the 1950s to 1960s and was subsequently prohibited. Many complications arise from silicone injection, and liquid silicone migration is a complication that has not been widely reported. The authors present magnetic resonance images of a patient with liquid silicone migration from the breast to the upper chest and lower neck. Breast ultrasonographic and mammographic findings are also presented for correlation.

Adult↗
PubMed1990

Histologic changes and silicone concentrations in human breast tissue surrounding silicone breast prostheses.

Using a previously developed method for quantitative measurements of silicone concentrations in breast tissue, material from 86 biopsies from 67 breasts in 55 patients who had silicone implants was examined. In the 49 breast with unruptured prostheses, there was a positive relation between the concentrations and inflammatory reactions, the only exception being the amount of plasma cells, which showed a negative relation. It is concluded that silicone prostheses provoke an inflammatory response not only because they act as foreign bodies, but also because of silicone seepage through intact membranes.

Breast↗
PubMed1998

The use of silicone occlusive sheeting (Sil-K) and silicone occlusive gel (Epiderm) in the prevention of hypertrophic scar formation.

The development of hypertrophic scars and keloids is an unsolved problem in the process of wound healing. For this reason, a successful treatment to prevent excessive scar formation still has not been found. Over the last decade, however, a promising new treatment has been introduced. Silicone materials have proved to reduce the amount of scar tissue and are believed even to prevent hypertrophic scar and keloid formation. In this study, the prophylactic effect of a silicone occlusive sheeting (Sil-K, Degania, Israel) and a silicone occlusive gel (Epiderm, Inamed B.V., The Netherlands) was investigated in a bilateral breast-reduction scar model in which the nontreated scars were supported by nonocclusive Micropore (3M, The Netherlands). The inframammary scars of 129 female patients with a mean age of 31 years ( 14 to 69 years) were studied up to 1 year after the operation. The width and height were measured, and B-scan ultrasound, laser-Doppler flowmetry, and color measurements were used as objective indicators to distinguish between normal and exuberant scars. Three months following the operation, 64.3 percent of the patients developed a hypertrophic scar, which was reduced to 56.6 percent after 6 months and down to 35.3 percent after 1 year. No keloids were seen. Patients with an easily tanning skin, nonsmokers, and patients with an allergy showed more hypertrophic scar formation. Neither Sil-K, used in 68 patients, nor Epiderm, used in 61 patients, could prevent the formation of hypertrophic scars. If both groups were taken together, the scars treated with silicone materials even developed significantly more hypertrophy compared with the Micropore-applicated scars.

Adolescent↗
PubMedDate not supplied

Enamel silicon and fluoride relationships demonstrating a surface silicon effect that facilitates fluoride uptake.

This study indicated that a clear relationship exists between silicon and fluoride. We have also demonstrated a probable surface enamel silicon effect that increases fluoride uptake. The complex set of relationships described in the surface chemistry of calcium, tin, and zirconium with fluoride, hydroxide, phosphate, and other surface-occurring ions need not be considered to confuse the specific silicon-fluoride relationship presented here because in this computation we are relating the changes in the silicon and fluoride ion values only. We have, however, considered the thermodynamics of such reactions and intend to elaborate on it in a later publication. We are aware of the small depth of fluoride penetration into enamel after topical treatment Health Foundation, Research Unit at the National Bureau of Standards, Washington, DC 20034, USA.

Composite Resins↗
PubMed2003

[Silicone breast implants with silicone gel and autoimmune disease--are they related?].

Silicone breast implants are used for breast reconstruction and breast augmentation. In the late 80's anecdotal literature describing a possible connection between silicone gel filled breast implants and autoimmune disease accumulated. Emerging concern about the safety of silicone gel implants had led the FDA to restrict their use. The continued use of the implants in postmastectomy reconstruction was allowed, as was their use in a small number of breast augmentation patients who were willing to enroll in long-term studies. In recent years, large meta-analyses established the fact that there is no association between silicone gel breast implants and autoimmune disease. We review the current literature, emphasizing the most important epidemiologic studies.

Autoimmune Diseases↗
PubMed1977

Silicone lymphadenopathy and synovitis. Complications of silicone elastomer finger joint prostheses.

We report two complications of silicone elastomer finger joint prostheses. In one patient, the prostheses broke, with silicone particles present in synovium ("detritic synovitis"). In another patient, silicone particles were found in an axillary lymph node five years after insertion of prostheses in the ipsilateral hand (prostheses were intact at the time). Microscopically, silicone particles in synovium and lymph node were identical to particles abraded from a new prosthesis.

Arthritis, Rheumatoid↗
PubMed2001

Tautomeric equilibrium between penta- and hexacoordinate silicon chelates. A chloride bridge between two pentacoordinate silicons.

The reaction of O-trimethylsilyl-1,1-dimethyl-2-trifluoroacetylhydrazine (1a) with chloromethyl(methyl)dichlorosilane affords an unexpected equilibrium mixture, 10a right arrow over left arrow 11a, between a neutral hexacoordinate silicon chelate with a covalent chloro ligand (10a) and an ionic pentacoordinate silicon complex (11a). The equilibrium reaction consists formally of a migration of the covalent chloro ligand from silicon to an adjacent ammonium nitrogen, as a chloride anion, and thus constitutes a novel type of tautomeric reaction. Crystallographic and NMR data provide evidence for the reaction. Temperature, solvent, substituent, and counterion effects on the tautomeric equilibrium are discussed: when the temperature of the mixture is raised, the equilibrium ratio 10a/11a increases. Formation of the mixture in toluene, a nonionizing solvent, shifts the equilibrium completely toward the neutral 10a. When the initial hydrazide has a phenyl (11c) or a hydrogen (11b) group as substituent, rather than CF3, the equilibrium is shifted to the ionic side. Replacement of the chloride counterion by triflate, using trimethylsilyl triflate, shifts the 10a/11a mixture to the ionic side. Low-temperature NMR monitoring of the stepwise formation of 10/11 was carried out and provided insight into the reaction mechanism. In an attempt to grow crystals of 11c, the pentacoordinate tautomer analogue, an unprecedented chloride-bridged disiloxane complex, with two pentacoordinate silicons sharing a common axial chloro ligand, crystallized and was characterized and described.

Journal Article↗
PubMed2004

Improved interatomic potentials for silicon-fluorine and silicon-chlorine.

Improved sets of empirical interatomic potentials for silicon-fluorine and silicon-chlorine are presented. The Tersoff-Brenner potential form has been reparameterized using the density-functional theory (DFT) cluster calculations of Walch. Halogenated silicon cluster energetics computed with DFT are, on average, within several tenths of an eV of the energies of the corresponding clusters with the reparameterized empirical potential for both Si-F and Si-Cl. Using the reparameterized Tersoff-Brenner potentials, molecular-dynamics simulations of F and Cl atom exposure to undoped silicon surfaces are in excellent agreement with published data on etch probability, halogen coverage at steady state, and etch product distributions.

Journal Article↗
PubMed1984

Covalent coupling of polysaccharides to silicon and silicon rubber surfaces.

A method to produce a hydrogel by covalently coupling dextran polysaccharide to silicon and silicon rubber surfaces is described. A bifunctional epoxysilane was used as coupling mediator and the conditions for the reaction were optimized. Coupling of the silane to silicon rubber was possible only after oxidation of the surface by plasma etching. The reaction between the epoxy-group and dextran was concentration dependent and required high concentrations of dextran. The turnover rate of fibrinogen in solution at the hydrophilic surface was found to be high when measured by ellipsometry.

Adsorption↗
PubMed2000

Silicone oil removal from a silicone intraocular lens with perfluorohexyloctane.

Silicone oil can be easily dissolved in vivo from silicone intraocular lenses by perfluorohexyloctane. Using specular microscopy, we examined the corneal endothelium in a patient with silicone lens implantation immediately after cataract surgery and 5 weeks postoperatively. There were no signs of acute or chronic toxicity to the endothelium.

Cataract Extraction↗
PubMed1996

Silicone granuloma in acral skin in a patient with silicone-gel breast implants and systemic sclerosis.

A 68-year-old white woman was referred to us by her rheumatologist for possible participation in a clinical study of photopheresis for scleroderma. In February 1993, she noticed edema of her distal phalanges, Raynaud's phenomenon in both hands, flu-like symptoms, fatigue, intermittent diarrhea, abdominal pain, tearing in both eyes, dyspnea on exertion, dysphagia, and odynophagia. Bilateral silicone-gel breast implants had been placed 12 years before; 2 months before her present evaluation, they were removed and found to be ruptured. Physical examination revealed edema, limited to the fingers and hands bilaterally, and slight induration of the skin on the dorsum of both hands and distal forearms. The remainder of the physical examination was normal. According to our study protocol, a skin biopsy specimen from the dorsum of the right hand was taken, but all other laboratory investigations were refused. Histopathologic examination revealed multiple clear spaces of varying sizes in the dermis and multinucleated macrophages containing small refractile particles, characteristic of silicone granuloma (Figs. 1 and 2); however, the specimen showed no evidence of scleroderma. X-ray energy dispersive analysis by scanning electron-microscopy confirmed the presence of elemental silicon in the small refractile particles. The patient did not receive any treatment after her diagnosis and shortly thereafter, she was lost to follow-up.

Aged↗
PubMed1992

Vitrectomy with silicone oil or perfluoropropane gas in eyes with severe proliferative vitreoretinopathy: results of a randomized clinical trial. Silicone Study Report 2.

Between September 1987 and October 1990, 265 eyes with rhegmatogenous retinal detachment and severe (with a classification of at least C-3) proliferative vitreoretinopathy were treated with vitrectomy and randomized to treatment with perfluoropropane gas or silicone oil; 131 eyes had undergone no prior vitrectomy (group 1) while 134 eyes had undergone vitrectomy with intraocular gas tamponade (group 2). At the last examination, there were no differences between perfluoropropane gas and silicone oil in achieving visual acuity greater than or equal to 5/200 (43% vs 45% for group 1, 38% vs 33% for group 2) and complete posterior retinal reattachment (73% vs 64% for group 1, 73% vs 61% for group 2). For group 1 eyes followed up for at least 18 months, there was an advantage favoring perfluoropropane gas in achieving complete posterior retinal reattachment (83% vs 60% at 36 months, P = .045). The rates of reoperation and keratopathy were similar, while hypotony was more prevalent in eyes randomized to perfluoropropane gas (group 2). Regardless of tamponade, groups 1 and 2 had similar anatomic and visual success. However, hypotony was twice as prevalent in group 2 (perfluoropropane), and the prevalence of keratopathy increased with follow-up in group 2 (either tamponade). Either tamponade produced better results than those seen with sulfur hexafluoride gas (Silicone Study Report 1).

Adult↗
PubMed2000

Silicon-based microelectrodes for neurophysiology, micromachined from silicon-on-insulator wafers.

A process is described for the fabrication of silicon-based microelectrodes for neurophysiology using bonded and etched-back silicon-on-insulator (BESOI) wafers. The probe shapes are defined without high levels of boron doping in the silicon; this is considered as a step towards producing probes with active electronics integrated directly beneath the electrodes. Gold electrodes, of 4 microns by 4 microns to 50 microns by 50 microns are fabricated on shanks (cantilever beams) 6 microns thick and which taper to an area approximately 100 microns wide and 200 microns long, which are inserted into the tissue under investigation. The passive probes fabricated have been successfully employed to make acute recordings from locust peripheral nerve.

Animals↗
PubMed1990

Silicone rubber-hydrogel composites as polymeric biomaterials. I. Biological properties of the silicone rubber-p(HEMA) composite.

A composite material was prepared consisting of silicone rubber matrix and particulate lightly cross-linked poly(2-hydroxyethyl methacrylate) (p(HEMA] hydrogel. The material resembling common silicone rubber is hydrophilic and swells in water like hydrogels. The effects of the implanted composite on tissues of the living organism were tested in rats by methods assessing local acute and chronic inflammatory reactions and calcification by means of radioactive indicators and by histological examination. Results of a 6 month implant study indicated no difference in reactions of the animal body on the silicone rubber-p(HEMA) composite and a non-toxic, non-irritant pure solid p(HEMA) control.

Animals↗
PubMed1980

Silicone lymphadenopathy: a complication of silicone elastomer finger joint prostheses.

Two cases of lymphadenopathy resulting from a lymph node foreign body reaction to silicone are presented. In each case lymph node biopsy was performed because of the clinical suspicion of neoplastic disease. Histologic study in both cases revealed no evidence of malignant disease, but rather demonstrated multinucleated giant cells in reaction to irregular fragments of refractile foreign material. The foreign substance was consistent in appearance with silicone. In each case a history of long standing rheumatoid arthritis and previous joint replacement with implantation of silicone elastomer prostheses was elicited.

Female↗
PubMed2002

A dynamic mechanical method for determining the silicone elastomer solubility of drugs and pharmaceutical excipients in silicone intravaginal drug delivery rings.

The silicone elastomer solubilities of a range of drugs and pharmaceutical excipients employed in the development of silicone intravaginal drug delivery rings (polyethylene glycols, norethisterone acetate, estradiol, triclosan, oleyl alcohol, oxybutynin) have been determined using dynamic mechanical analysis. The method involves measuring the concentration-dependent decrease in the storage modulus associated with the melting of the incorporated drug/excipient, and extrapolation to zero change in storage modulus. The study also demonstrates the effect of drug/excipient concentrations on the mechanical stiffness of the silicone devices it 37 degrees C.

Biocompatible Materials↗