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PubMed1996

Polyurethane versus silicone for endoprosthetic replacement of the metacarpophalangeal joints in rheumatoid arthritis.

In a prospective study 12 patients with rheumatoid arthritis underwent arthroplasty of four metacarpophalangeal joints. Two different implant materials were randomly used in each hand, polyurethane (Pellethane) or silicone (Silastic). Eleven patients with 44 (21 silicone; 23 polyurethane) implants were re-examined 4.5 years (range 3-5) postoperatively. No difference was found between the implant materials regarding pain, stability of the joint or recurrence of the ulnar drift. The mean range of motion was 41 degrees (range 20 degrees-70 degrees) in the polyurethane joints compared with 42 degrees (range 15 degrees-90 degrees) in the silicone joints. The extension deficit was more pronounced in the silicone (mean 11.4 degrees) than in the polyurethane (mean 5.8 degrees) joints, and clinical signs of synovitis around the implants were more common with the silicone arthroplasties. Radiographic analysis, performed with conventional radiography and computed tomography (CT) showed one implant fracture in each group. There was a more pronounced bone resorption around silicone implants, but more sclerosis around polyurethane implants. Bony spurs interfering with function of the implant were common with both materials.

Aged↗
PubMed1999

RTV silicone elastomers in hand prosthetics: properties, applications and techniques.

In this technical note, an overview of RTV (room-temperature-vulcanising) silicone elastomers is provided. The properties and applications of 3 different types of RTV silicones in producing prostheses for the hand are discussed. Vinyl polysiloxanes are excellent silicone impression materials that offer the advantages of a rapid cure, near exact duplication of fine details and ease of removal of the cured impression without permanent deformation. RTV-2 dimethyl polysiloxanes are ideal for mould-making and fabricating prostheses given their favourable qualities that range from ease of pigmentation, adjustable consistency, manageable curing rate and accuracy in recording fine details in the liquid state to excellent stain-resistance, elasticity and biodurability in the vulcanised state. RTV-1 dimethyl polysiloxanes are self-curing, ready-for-use silicones that adhere adequately well to most substrates and are useful for extrinsic hue modifications and waterproofing of the prosthesis. The basic techniques for each of these applications are also discussed. The cure-inhibition of addition-curing RTV silicones by sulphur-, tin- and nitrogen-containing contaminants and its damaging consequence is highlighted. A compilation of known contaminating agents is provided so that prior contact with these objects can be avoided when working with addition-curing silicones. The precautionary measures to prevent the problem are also outlined.

Elasticity↗
PubMed2000

Silicone oil and fluorosilicone.

Silicone oil has been used to fill the vitreous cavity for long-term or permanent internal tamponade in eyes with proliferative vitreoretinopathy or complicated retinal detachment due to ocular trauma, giant retinal tears, proliferative diabetic retinopathy, and cytomegalovirus retinitis. Reports from the Silicone Study confirmed its efficacy in the treatment of proliferative vitreoretinopathy and addressed outcome differences in vitrectomized and nonvitrectomized eyes, combined retinotomy, silicone oil removal, and complications associated with silicone oil tamponade, such as intraocular pressure abnormalities and corneal abnormalities. Because silicone oil is lighter than water and not adequate in supporting the inferior quadrants, several heavier-than-water materials have been introduced for intraocular tamponade. Silicone oil can be a potential vehicle for delivering antiproliferative agents to treat proliferative vitreoretinopathy.

Humans↗
PubMed1982

Biocompatibility of a silicon based peripheral nerve electrode.

The biocompatibility of a silicon neuroelectric interface for chronic use in mammalian peripheral nerves was investigated. New Zealand white rabbits were used as the animal model. The implant was made of (110) silicon coated with one micron of silicon dioxide. An anisotropic etch was used to form a grid of ten silicon bars each 40 microns wide and spaced 160 microns apart. A Silastic nerve cuff was molded onto each side of the grid. Using microsurgical techniques, the nerve was transected and sutured into the implant cuff. One implanted rabbit was completely analyzed and is reported here. By 32 days post operatively, the EMG of the affected muscles had partially recovered. The EMG of the affected muscles was indistinguishable from the contralateral control muscles after 150 days. At 332 days, the conduction properties of the implanted nerve confirmed that the nerve was capable of conduction through the silicon grid. Histological observations were consistent with normal peripheral nerve regeneration following microsurgical neurrorhaphy. Seven additional rabbits have been implanted and will be fully analyzed in the future. It was concluded that the silicon peripheral nerve implant described here should be pursued as a substrate for a chronic neuroelectric interface.

Animals↗
PubMed1997

Enhancing nerve regeneration across a silicone tube conduit by using interposed short-segment nerve grafts.

Isolated nerve segments may inherently contain all of the necessary factors required to support regeneration within a silicone tube conduit placed across a nerve gap. Thirty-six adult Lewis rats each weighing approximately 250 g were randomized into three groups. A sciatic nerve gap (13-15 mm in length) was bridged by an empty silicone tube (Group I), a silicone tube containing a short 2-mm interposed nerve segment (Group II), or a nerve autograft (Group III). At 16 weeks postoperatively, no regeneration was observed through the empty silicone tube. In contrast, regeneration across the silicone tube containing the isolated nerve segment was equivalent to that noted through nerve autografts as assessed by histological, electrophysiological, and functional criteria. Thus, an interposed nerve segment will extend the length of successful nerve regeneration through a silicone tube conduit.

Action Potentials↗
PubMed2005

Distal ventriculoperitoneal shunt failure caused by silicone allergy. Case report.

The placement of a ventriculoperitoneal (VP) shunt is the most common form of treatment for hydrocephalus. Although allergic reactions to the silicone in shunt hardware are very rare, the authors describe a case of silicone allergy causing multiple ventricular shunt revisions. A 24-year-old man, who had undergone multiple VP shunt revisions, presented with shunt malfunction caused by allergic reaction of the tissues surrounding the shunt tubing. The patient's existing silicone-based shunt was replaced with a new polyurethane system, including the proximal and distal catheters as well as the valve mechanism. Contrary to recommendations in previous studies of silicone shunt allergies, long-term immunosuppression was not initiated. The patient was followed up for more than 8 years without recurrence of an allergic reaction to the shunt. This outcome indicates that replacing the original silicone-based shunt system with a polyurethane-based system alone is sufficient in the treatment of a silicone shunt allergy.

Adult↗
PubMed1998

Subconjunctival silicone oil drainage through the Molteno implant.

To describe silicone oil drainage from the vitreous cavity to the subconjunctival space through a Molteno implant. A 52-year-old aphakic man with a Molteno implant inserted after lensectomy, vitrectomy and intravitreal silicone oil injection visited our hospital. The Molteno tube was located in the anterior chamber with two silicone oil drops on it. Corneal dellen, induced by marked bleb-like elevation of the conjunctiva was noted during follow-up and excision biopsy was attempted. The conjunctival elevation consisted of innumerable microdrops of silicone oil enclosed by inflammatory subconjunctival tissue. Silicone oil as well as aqueous humor had drained through the Molteno implant and glaucoma implant surgery may thus not be appropriate for the control of intraocular pressure of aphakia by intravitreal silicone oil before removal of oil.

Aphakia, Postcataract↗
PubMed1978

[Residual radioactivity measurement for high purity silicon irradiated by pile-neutron (author's transl)].

Residual radioactivity measurement is described for high purity silicon (purer than tennine) irradiated by pile-neutron to produce n-type silicon semiconductor. The silicon samples were irradiated in four different atomic reactors with thermal neutron fluxes of 0.12, 1.48, 1.8 and 5.5 X 10(13) n/cm2. sec. After irradiation, the sample was dissolved in HF-HNO3, and the solution dried. The residual radioactivity was measured by a 2pi gas-flow low background GM counter. The only active species found was 32P, which was formed by the consecutive reaction of 30Si(n, gamma)31Si beta- leads to 31P followed by 31P(N, GAMMA)32P. The observed production rate for 32P was in good agreement with the calculated one. This technique can be applied to estimate amounts of not only doped phosphorus but impurities such as gold in irradiated silicon. Tail part of a float-zone silicon rod contained about 0.01 atomic ppb of Au, but no activity was observed in its middle part. The present technique is suitable for checking and characterizing silicon rods before their neutron-doping.

Neutrons↗
PubMed1998

[Silicon of the medium in the postoperative maxillary cyst].

As part of a study on chronic inflammatory disease of the mucous membrane, silicon of the medium in postoperative maxillary cysts and in other cysts was measured, and following results were obtained. Silicon concentrations of the medium in the postoperative maxillary cysts and in the postoperative ethmoidal cysts were 34.5 ppm and 42.9 ppm (geometrical mean) respectively, and they were higher than in other primary cysts such as frontal cyst, nasal vestibular cyst, and dental cyst. The silicon content of the medium in the postoperative maxillary cyst varied with the water content of the medium; the lower the water content the higher was the silicon content and the relationship was expressed by the following equation. log S = 7.43 + 7.14 log d-6.14 log w, where S = Si (mcg), d = dry weight (g.) and w = wet weight (g.). The high concentration of silicon in the postoperative cyst was considered to be due to the large amount of silicon transudate from the surrounding fibrous tissue through a highly damaged or missing epithelial wall of the cyst.

Cysts↗
PubMed1980

Sustained release of niridazole from silicone rubber implants for the treatment of Schistosoma mansoni infections.

Niridazole was incorporated into silicone rubber implants to investigate the potential of a sustained release of the drug in the therapy of murine schistosomiasis mansoni. The infected animals (200 cercariae for 6 weeks) were randomly divided into three groups: one group received silicone rubber implants containing 50% by weight niridazole; a second group received blank silicone rubber implants with no drug; and the third group received no implants. Mortality 4 weeks later was in excess of 80% for animals with no implants or with the blank silicone rubber implants. In contrast, 10% mortality was observed in the mice receiving the niridazole-silicone rubber implants over a 10-week period. The worm burden in the niridazole-silicone rubber implant group was reduced at 10 weeks post implantation by 77%.

Animals↗
PubMed1993

A clinical and immunologic evaluation of women with silicone breast implants and symptoms of rheumatic disease.

OBJECTIVE: To describe the clinical and serologic features of women with silicone breast implants who were referred for symptoms of rheumatic disease. DESIGN: A case series. SETTING: University and private rheumatology practices. PATIENTS: A total of 156 women with silicone breast implants and rheumatic disease complaints. Controls for the serologic studies included women with silicone implants and no rheumatic symptoms (n = 12) and women with fibromyalgia without silicone implants (n = 174). MEASUREMENTS: Complete physical examination and testing for immunoglobulins; complement; C-reactive protein; rheumatoid factor; and autoantibodies by indirect immunofluorescence, immunodiffusion, and Western blot. RESULTS: Three subgroups of patients were defined based on clinical and laboratory findings: joint and muscle pain (n = 95), joint swelling (n = 32), and connective tissue disease (n = 29). Most women had normal immunologic studies. The patients with joint swelling had mild, asymmetric, rheumatoid-factor-negative synovitis that did not meet American College of Rheumatology criteria for rheumatoid arthritis. Fourteen patients had a scleroderma-like illness and anti-centromere or anti-PM-Sci antibodies by Western blot. Ten patients had a positive Western blot for BB' polypeptide, a small nuclear ribonucleoprotein (snRNP), but did not meet criteria for systemic lupus erythematosus. No autoantibodies to known disease-related polypeptides were detected on Western blot in the control groups. CONCLUSION: Most women with silicone implants and rheumatic complaints had normal results of serologic tests and nonspecific symptoms, suggesting no serious connective tissue disease. However, a subset of women had clinical signs and serologic tests that were unusual even for referred patients. These observations suggest, but cannot establish, that some women with silicone breast implants may develop atypical immunologic reactions.

Adult↗
PubMed1996

Reported complications of silicone gel breast implants: an epidemiologic review.

PURPOSE: To review the range of local and systemic complications attributed to silicone breast implants and to evaluate the epidemiologic literature on these complications. DATA SOURCES: Epidemiologic studies of the potential risks of silicone breast implants identified by MEDLINE search and literature review. STUDY SELECTION: Epidemiologic studies with cohort, case-control, and cross-sectional designs. When epidemiologic studies were unavailable (as for estimates of local complications), case series were reviewed. DATA EXTRACTION: Epidemiologic studies evaluated for methodologic quality, including such characteristics as study design, sample size and selection, determination of silicone exposure and outcome variables, and duration of follow-up. DATA SYNTHESIS: The epidemiologic literature on the potential complications of silicone breast implants has concentrated primarily on connective tissue disorders and cancer. Estimated of the true incidence of local complications, such as rupture, capsular contracture, and breast pain, are unavailable. Studies of scleroderma and other defined connective tissue diseases suggest that implant recipients have no substantially increased risk for these disorders; however, the epidemiologic literature is insufficient to rule out an association between breast implants and connective tissue disease-like syndromes. Overall, the rate of breast cancer does not seem to be increased in women with silicone breast implants. However, the risk to women as they reach the postmenopausal years in not yet known. CONCLUSIONS: Information is insufficient to adequately advise women who currently have or are seeking to obtain breast implants about the overall risk of these devices. No epidemiologic study has indicated that the rate of well-defined connective tissue disease or breast cancer has greatly increased in women with silicone breast implants, but no studies have ruled out a moderately increased risk for these diseases. No studies have adequately addressed the crucial issue of local complications such as rupture and capsular contracture, although evidence increasingly points to a higher risk for rupture as implants age.

Breast Implants↗
PubMed2000

Textured-surface saline-filled silicone breast implants for augmentation mammaplasty.

The earliest silicone breast implants were smooth-surface, silicone rubber devices filled with either silicone gel or saline. Because of persistent problems with capsular contracture, polyurethane-covered silicone implants were developed as an alternative. Particularly in the short run, these alternatives proved highly successful at reducing the incidence of capsular contracture. By 1990, polyurethane-covered implants were rapidly becoming the preferred implant choice of many plastic surgeons, but for legal, regulatory, financial, and safety reasons they were withdrawn from the market by Bristol-Myers in 1991. Meanwhile, during the late 1980s, surface texturing and improved materials became available on other silicone breast implants and expanders. Most studies suggest that textured-surface silicone gel-filled implants, saline-filled implants, and tissue expanders have less frequent capsular contracture than their smooth-surface counterparts.

Breast Implants↗
PubMed2001

[Treatment of retinal re-detachment in eyes with intraocular silicone oil].

PURPOSE: To describe the standardized surgical technique we used to treat recurrent retinal detachment in eyes that had been previously operated on with silicone oil. METHOD: We present 6 cases in which the following surgical steps were carried out as a standardized procedure: 1) silicone oil extraction, 2) partial introduction of perfluorcarbon liquids (PFCL), 3) extraction of epiretinal membranes, 4) endodiathermy, 5) retinotomy, 6) retinectomy, 7) complete filling of the intraocular cavity with PFCL, 8) endophotocoagulation and 9) 5,000 Cs silicone oil injection. RESULTS: All the patients maintained the reattached retina. Five of them still have the silicone oil in the vitreous cavity. One patient suffered a macular epiretinal membrane. A second patient presented a macular epiretinal membrane with subfoveal PFCL as well as a relapse of the retinal re-detachment when we extracted the silicone oil during the macular surgery, so that it had to be re-introduced. All of the patients, except two who were aphakic, developed different degrees of cataracts. CONCLUSIONS: The systematic use of these surgical steps can be very useful in the management of retinal detachment relapses in eyes previously treated with silicone oil injection.

Adult↗
PubMedDate not supplied

The use of x-ray fluorescent spectroscopy to study the influence of cationic polymers on silicone oil deposition from shampoo.

In this study, x-ray fluorescent spectroscopy was employed, in a non-destructive way, to analyze the influence that water-soluble, cationic hydroxyethylcellulose (i.e., polyquaternium-10) has on the deposition of silicone oil (dimethicone) onto hair. Virgin brown hair tresses were washed with various model shampoos that contained emulsified dimethicone. The shampoos were modified only by the addition or absence of polyquaternium-10. The results indicate that the cationic polymers do influence silicone oil deposition onto hair during the shampooing process. In the absence of cationic polymer, the silicone oils deposit readily, but appear to show "build-up" phenomena upon repeated washings. When a cationic polymer is present in the continuous phase of the shampoo, the build-up phenomena is significantly diminished, and silicone oil deposition remains relatively constant in repeated washings. In addition, we have noted that the molecular weight of the cationic polymer can have a strong effect on silicone oil deposition. It appears that the higher the molecular weight of the polyquaternium-10, the greater the amount of silicone deposition onto the surface of the hair. To demonstrate that the analysis technique has potential applications in commercial shampoos, we examined a commercial "2-in-1" shampoo that contains dimethicone and polyquaternium-10 and found that the data for our simple model shampoos and the commercial shampoo correlated closely.

Cations↗
PubMed2001

[Histologic evaluation in rabbits of the biocompatibility of episcleral implant material: S-PTFEe (silicone core covered with expanded polytetrafluoroethylene)].

PURPOSE: To study the tolerance of a silicone band wrapped with expanded polytetrafluoroethylene (e-PTFE) in "fauve de Bourgogne" rabbits. METHODS: A 5.7mmx3.2mm band of S-PTFE (silicone-polytetrafluoroethylene, France Chirurgie Instruments) was used. A tight seal was produced between the two materials by silicone gluing. Eight eyes were implanted episclerally and fixed with Mersilene 5-0. One silicone band was used on a control eye. RESULTS: Three eyes were removed at 4 weeks, one at 8 weeks and four at 12 weeks. No extrusion was observed except for the silicone band rejected 2 weeks after implantation. On histopathologic examination, PTFE colonisation was present in all eyes with fibroblast, inflammatory cells, and neovascularization. CONCLUSION: The S-PTFE implant was colonized and well tolerated in rabbit eyes. Advantages of silicone band (quality, stability of indentation) are combined to the tolerance of PTFE.

Animals↗
PubMed1975

A long-term evaluation of silicone retinopathy in monkeys.

Six owl monkeys were exposed intravitreally for 6 to 28 months to Dow Corning Medical Fluid 350 in a morphologic study of silicone retinopathy. Fellow eyes of each silicone-injected animal and six eyes from three normal untreated monkeys served as controls. In addition, two eyes were treated post-mortem with silicone oil to insure that no artefact redistribution occurred. Each case was studied histochemically in frozen sections, with electron microscopy of Epon-embedded materials. All silicone-injected eyes showed numerous empty spaces in the inner segment of the retina adjacent to the vitreoretinal interface, corresponding to the intercellular spaces between Müller's filbers. These spaces contained numerous spherical bodies encircled by a homogeneous electron-opaque material, suggesting a silicone-phospholipid complex. Marked degeneration of small ganglion cells was seen. Müller's fibers appeared to be shrivelled. The lack of phospholipids in the inner segment of the visual receptors was marked, although no significant morphologic lesions were detectable. Abnormally high ATPase activity was found in both plexiform layers. There were no such lesions in the untreated control eyes, nor any detectable artefactual redistribution of silicone oil in the eyes treated post-mortem with Medical Fluid 350.

Alkaline Phosphatase↗
PubMed2002

Evaluation of optical changes of three types of lenses: hard PMMA, hydrogel, and heparin surface modified hard lenses effected by silicone oil, used clinically as a substitute of the vitreous body.

The objective of these investigations was an in vitro evaluation whether silicone oil OXANE of viscosity 5700 cSt clinically used in eye surgery as a substitute of the vitreous body, being in contact with an artificial polymer lens used as an implant of human lens, causes the changes in its optical properties. The paper presents the results of spectral analysis of transmission of visible (VIS) radiation of three types of artificial lenses: hard PMMA, hydrogel, heparin surface modified (HSM) hard PMMA, and the same lenses damaged by YAG laser radiation with an energy increasing from 1.7 mJ to 3.7 mJ, exposed to clinically applied silicone oil. The studies were carried out, in two-week intervals, over a period of 20 weeks. Hard PMMA and HSM lenses were found not to have changed their optical properties after 20 weeks of exposure to silicone oil. The measured transmittance values were within the range of instrumental error (+/- 1%). Optical properties of hydrogel lenses exposed to silicone oils deteriorated with exposure and after 20-week exposure to silicone oil the average transmittance value decreased by about 18%, reaching its final value of 67.08 +/- 2.37% (RSD = 5.56%). A minimal decrease of the initial transmittance values was observed only for the lenses exposed to laser radiation of highest energy (3.7 mJ). After completed exposure to silicone oil, two kinds of lenses were found to have a slightly improved transmittance: hard PMMA lenses by about 4% and HSM lenses by about 2%. On the other hand, in case of hydrogel lenses the deterioration of optical properties to the extent comparable to that of hydrogel lenses not damaged by laser radiation was observed.

Heparin↗