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PubMed1995

Elevated serum silicon levels in women with silicone gel breast implants.

The metabolic fate of silicone gel leaked from an intact or ruptured prosthesis is unknown. In this study, serum was blindly assayed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) for elemental silicon in 72 women with silicone gel breast implants and 55 control women (mean age 48 yr, both groups). Blood was drawn and processed using silicon-free materials. The mean silicon level in controls was 0.13 +/- 0.07 mg/L (range 0.06-0.35 mg/L), whereas in implant patients, the mean was significantly higher at 0.28 +/- 0.22 mg/L (range 0.06-0.87 mg/L) (P < 0.01, Student's t-test with correction for unequal variances). Using the mean of the control group + 2 SD as a cutoff for normal range (0.27 mg/L), 25/72 (34.7%) implant patients exceeded this value, compared with 2/55 (3.6%) controls. There was no significant correlation between past rupture of one or both implants, current rupture at the time of the blood draw, or the number of years with implants and silicon levels. The results suggest that serum silicon levels are elevated in many women with silicone gel breast implants. The chemical species involved and kinetics of this elevation remain to be determined.

Breast Implants↗
PubMed1997

Vitrectomy with silicone oil or long-acting gas in eyes with severe proliferative vitreoretinopathy: results of additional and long-term follow-up. Silicone Study report 11.

BACKGROUND: The Silicone Study evaluated the outcomes of vitreoretinal surgery for retinal detachment with proliferative vitreoretinopathy (PVR). OBJECTIVE: To evaluate short-term (up to 36 months) outcomes in eyes randomized to silicone oil or perfluoropropane gas and long-term (up to 72 months) outcomes in eyes with attached maculas at 36 months. DESIGN: Prospective, randomized, multicentered surgical trial. SETTING: Community- and university-based vitreoretinal practices. PATIENTS: Two-hundred sixty-five eyes with PVR randomized to perfluoropropane gas and silicone oil with follow-up through 3 years (cohort 1) and 249 eyes with attached maculas at 36 months (121 eyes randomized to long-acting gas [either sulfur hexafluoride or perfluoropropane] and 128 eyes randomized to silicone oil) with follow-up up to 6 years (cohort 2). Both cohorts consisted of eyes that had and had not undergone vitrectomy for PVR (groups 1 and 2, respectively) before randomization. Of the 265 eyes in cohort 1, 24-month follow-up data were available for 218 eyes (82%) and 36-month follow-up data were available for 196 eyes (74%). Of 208 eyes in cohort 2, 48-month follow-up data were available for 146 eyes (70%), 60-month follow-up data for 119 eyes (57%), and 72-month follow-up data for 73 eyes (35%). INTERVENTIONS: Vitrectomy surgery for PVR with a long-acting gas or silicone oil as the intraocular tamponade. MAIN OUTCOME MEASURES: Changes in visual acuity, recurrent retinal detachment, and incidence of complications. RESULTS: In group 1 of cohort 1, compared with oil-treated eyes, gas-treated eyes had a higher rate of complete retinal reattachment from 18 to 36 months (P < .05). No other differences were found. In group 2 of cohort 1, no notable differences were found between treatment arms. In cohort 2, during 6 years of follow-up, attachment of the macula was maintained for all eyes. No notable differences in the rates of complete retinal attachment, visual acuity of 5/200 or better, or glaucoma were found between treatment groups. In contrast, gas-treated eyes had more hypotony (P < .001). Silicone oil-treated eyes that underwent subsequent surgery were more likely to have the oil retained (P = .02). Compared with oil-retained eyes, oil-removed eyes had higher rates of complete posterior attachment (P = .01) and of a visual acuity of 5/200 or better (P < .001) and less keratopathy (P < .05). Compared with oil-removed eyes, gas-treated eyes had a worse visual acuity outcome (P < .05) and more hypotony (P < .01). CONCLUSION: The Silicone Study showed that silicone oil and perfluoropropane gas were equal in most respects for the management of retinal detachments with PVR. Success in the first surgery for PVR is paramount for obtaining better visual results. Overall, surgery for PVR had a high likelihood of retinal reattachment, and if anatomically and visually successful at 3 years, there is an excellent chance that the results will be maintained over the long-term.

Adult↗
PubMed2005

Surface modification of silicon and gold-patterned silicon surfaces for improved biocompatibility and cell patterning selectivity.

Clean silicon and gold-patterned silicon platforms were modified with methoxy-polyethylene glycol (M-PEG silane) via a self-assembly technique, which significantly improved their plasma protein resistance capability and cell patterning selectivity. Fibrinogen and IgG were used as model plasma proteins to study the efficacy of PEG layers in resisting protein adsorption. Selective cell patterning on the gold regions of a gold-patterned silicon substrate and tissue compatibility were studied with macrophage and fibroblast cells. The research also revealed how the presence of gold electrodes on a silicon substrate would influence the cell patterning selectivity. Our experimental results showed that the PEG-modified silicon surfaces had a high resistivity to protein and cell attachment and that the PEG-modified gold-patterned silicon surfaces nearly completely eliminated the protein adsorption and cell attachment on silicon. This study provides a new approach to developing biocompatible surfaces for silicon-based BioMEMS devices, particularly for biosensors where a metal-insulator format must be enforced.

Adsorption↗
PubMed2006

Re-emergence of hidden residual intraocular silicone oil bubble after previous silicone oil removal.

BACKGROUND: We describe the re-emergence of a hidden residual intraocular silicone oil bubble after previous silicone oil removal. HISTORY AND SIGNS: A 57-year-old patient underwent vitrectomy with silicone oil for a complicated retinal detachment. Six weeks later silicone oil was removed via the pars plana and phakoemulsification with lens implantation was performed. Subsequent clinical follow-up showed an attached retina without residual silicone oil bubbles. However, more than 2 years later the patient suffered sudden visual loss. Clinical examination showed a bubble of silicone oil wedged between a remaining layer of anterior vitreous and the capsular bag, reducing central visual acuity. THERAPY AND OUTCOME: Complete extraction of the silicone oil bubble was performed via the pars plana. CONCLUSIONS: Residual silicone oil bubbles may wedge themselves into vitreous pockets in the ophthalmoscopically invisible regions of the pars plana. Over time these bubbles may migrate into the retrolental space with obstruction of the visual axis.

Drainage↗
PubMed1982

[Can silicon diffusion from silicone rubber catheters cause urethral stricture?].

Silicon-leakage out of alloplastic Silicon containing implants induces myofibroblast proliferation and constricting scar tissue. Therefore the possible Silicon-leakage out of Silicon rubber Foley-Catheters was of major interest. This cathaters were often used after internal urethrotomies of recurrent urethral strictures. Pieces of Silicon rubber Foley-Catheters of 18 F, 2 cm in length, were implanted subcutaneously and intraperitoneally in rats. Using Scanning electron microscopy and EDXA (energy dispersiv x-ray microanalysis) Silicon could not be identified in tissues around the implants 6 and 12 weeks after implantation. Therefore Silicon-leakage out of Silicon rubber Foley-Catheters is not responsible for recurrent urethral strictures.

Animals↗
PubMed2003

A stable silicon-based allene analogue with a formally sp-hybridized silicon atom.

Carbon chemistry exhibits a rich variety in bonding patterns, with homo- or heteronuclear multiple bonds involving sp-hybridized carbon atoms as found in molecules such as acetylenes, nitriles, allenes and carbon dioxide. Carbon's heavier homologues in group 14 of the periodic table--including silicon, germanium and tin--were long thought incapable of forming multiple bonds because of the less effective p(pi)-p(pi) orbital overlap involved in the multiple bonds. However, bulky substituents can protect unsaturated bonds and stabilize compounds with formally sp-hybridized heavy group-14 atoms: stable germanium, tin and lead analogues of acetylene derivatives and a marginally stable tristannaallene have now been reported. However, no stable silicon compounds with formal sp-silicon atoms have been isolated. Evidence for the existence of a persistent disilaacetylene and trapping of transient 2-silaallenes and other X = Si = X' type compounds (X, X' = O, CR2, NR, and so on) are also known, but stable silicon compounds with formally sp-hybridized silicon atoms have not yet been isolated. Here we report the synthesis of a thermally stable, crystalline trisilaallene derivative containing a formally sp-hybridized silicon atom. We find that, in contrast to linear carbon allenes, the trisilaallene is significantly bent. The central silicon in the molecule is dynamically disordered, which we ascribe to ready rotation of the central silicon atom around the molecular axis.

Journal Article↗
PubMed2000

Plasmon-loss imaging of chains of crystalline-silicon nanospheres and silicon nanowires

Nanostructures in chains of crystalline-silicon nanospheres and silicon nanowires were investigated using energy-filtered transmission electron microscopy (TEM). Observation of the shape of the silicon nanospheres in the chains provided the direct evidence that the chains were formed via the surface oxidation process, which may preferentially work at the necks. The diverse nanostructures in silicon nanowires were revealed, and we found smooth-shaped wires which have periodically modulated silicon cores. Nanostructures in wire-chain transition regions were also investigated for the first time. The wire-chain transition is not a simple junction of a silicon nanowire and a chain of silicon nanospheres, but has a periodically modulated silicon core in the wire region near the transition position.

Journal Article↗
PubMed2006

[Bonding structure in silicon nitride thin films containing silicon nano-particles].

Non-stoichiometric hydrogenated amorphous silicon nitride (a-SiNx : H) film was deposited by helico-wave plasma-enhanced chemical vapour deposition (HWP-CVD) technique. The microstructure and bonding characteristics of both as-deposited and annealed thin films were studied. Raman scattering measurement shows that excess silicon exists in the form of amorphous silicon particles in the as-deposited sample. The microstructure of crystalline nano-particles silicon embedded in silicon nitride matrix in the post-annealed sample was formed. Comparing the results of both the Fourier transform infrared spectra and the optical absorption spectra of the samples deposited under different conditions, it is shown that the microstructure of the thin film depended on the gas flow ratio and annealing process. The sample with lower excess silicon shows a lower density of defect state at the silicon nanocrystal/SiNx interface due to a higher binding hydrogen content. The annealing process induces the decrease in Si-H and N--H binding densities. Because of the formation of silicon nanocrystals, the annealed samples exhibit a higher structure disorder degree.

English Abstract↗
PubMed1998

29Si imaging of silicone breast implants and intraocular silicone oil.

Silicon-29 (29Si) imaging was investigated as a potential imaging modality for monitoring silicone prostheses in humans. The 29Si relaxation times of several silicone gels were measured and found to average T1 = 21.2 +/- 1.5 s and T2 = 207 +/- 40 ms, with no significant difference between virgin and explanted gels. A single-shot half-Fourier rapid acquisition with relaxation enhancement (RARE) and a refocused gradient-echo sequence were used for acquiring 29Si images with 5 x 5 mm2 resolution and no slice selection. Three volunteers with silicone-gel-filled breast implants and one subject with an intraocular silicone oil injection were thus examined in a total acquisition time of 10-15 min per image. On all 29Si images, the shape of the silicone object was well depicted. Although at present, conventional proton images are superior in resolution and signal-to-noise ratio, 29Si imaging has the advantage of optimal specificity, since only the silicone itself is visible.

Biocompatible Materials↗
PubMed1994

The effects of silicone oil removal. Silicone Study Report 6.

OBJECTIVE: To evaluate the advisability of removing silicone oil from eyes after surgery for severe (with a classification of at least C-3) proliferative vitreoretinopathy. DESIGN: Subgroup analysis of the Silicone Study, a randomized, multicentered, surgical trial. SETTING: Community- and university-based clinics. PATIENTS: Two hundred twenty-two eyes with severe proliferative vitreoretinopathy followed up in the Silicone Study. INTERVENTIONS: Vitrectomy for proliferative vitreoretinopathy with silicone oil as the intraocular tamponade. OUTCOME MEASURES: Changes in visual acuity, recurrent retinal detachment, and incidence of complications. RESULTS: Ninety-nine (45%) of 222 eyes had surgery for silicone oil removal (oil-removed eyes). Compared with the eyes that did not undergo silicone oil removal (oil-retained eyes) evaluated at a comparable time after oil injection, oil-removed eyes at the examination prior to oil removal were more likely to be attached (85% vs 40%; P < .0001), have a visual acuity of 5/200 or greater (63% vs 35%; P < .0001), and not be hypotonous (5% vs 22%; P < .001). There was no association between the length of oil retention and incidence of recurrent retinal detachment after oil removal. Eyes with attached retinas at the time of oil removal generally improved in visual acuity at the last follow-up examination (P < .0001), which was not evident in eyes with detached retinas at the time of oil removal. In a matched-pair cohort analysis comparing both sets of eyes, there was an increased risk for recurrent retinal detachment at the last follow-up examination in the oil-removed eyes (odds ratio [OR], 2.1; P = .09). However, overall visual acuity improved for oil-removed eyes in 19 (29%) of 66 pairs and for oil-retained eyes in one (2%) of 66 pairs (OR, 19.0; P < .0001). Although nonsignificant, incidence rates of keratopathy (OR, 0.5) and hypotony (OR, 0.5) were lower in oil-removed eyes. CONCLUSION: Removal of silicone oil in anatomically successful eyes significantly increases the likelihood of improved visual acuity with a slight increase in the likelihood of recurrent retinal redetachment. There was a trend for a reduction in the incidence of complications in the oil-removed eyes.

Adult↗
PubMedDate not supplied

MR imaging of silicone gel-filled breast implants in vivo with a method that visualizes silicone selectively.

The lack of an adequately sensitive method for detecting silicone leakage and reported serious complications due to silicone leakage were cited as justification by the U.S. Food and Drug Administration for imposing the current restrictions on silicone gel-filled breast prostheses. The authors report a new magnetic resonance imaging method for visualizing silicone leakage: the silicone-only sequence (SOS). The method uses the conventional STIR (short-inversion-time inversion-recovery) technique combined with a 1331 radio-frequency pulse train widely used for water suppression in spectroscopy. With the SOS, silicone can be imaged while signals from fat and water are suppressed. The authors used the SOS to image phantoms and normal and ruptured silicone gel-filled breast prostheses.

Breast↗
PubMed1993

Migration and biodegradation of free silicone from silicone gel-filled implants after long-term implantation.

In vivo 1H NMR chemical shift imaging (CSI), 1H NMR localized spectroscopy (STEAM) and multinuclear NMR spectroscopy (29Si, 13C, 1H) were used to characterize the aging process of silicone gel-filled implants in a rat model after long-term implantation. Although no significant changes could be observed in the implants or surrounding tissue by in vivo 1H chemical shift imaging, in vivo 1H localized spectroscopy of the livers from the longer term population revealed the presence of silicone. Ex vivo 29Si spectroscopy of the liver, spleen, and the capsule formed around the 9 and 12 month implants clearly demonstrated and confirmed for the first time that a significant amount of free silicone migrates from silicone gel-filled implants. Also, these results show that silicones are not metabolically inert, and their biodegradation in tissue and within the implant can be monitored after 9 and 12 months by changes in the 29Si chemical shifts seen in corresponding ex vivo spectra. The NMR findings are supported by those obtained by atomic absorption spectroscopy. Silicone aging changes not only the chemical composition of the gel, but also its proton T2 relaxation times, which increase with long implantation times. The three dimensional structure of the gel disintegrates (i.e., polymer chain rupture), increasing the molecular mobility of the polymer and, consequently, its protons T2 values. The relaxation data we obtained reflect this in vivo degradation, especially in the case of implant rupture. Additionally, small concentrations of fat in the silicone gel were found within the implants. The presence of these lipophilic substances also might increase the T2 values (plasticizer effect). These findings may assist in evaluating the implant integrity and disease symptoms related to their presence in humans.

Animals↗
PubMed2000

Anti-silicone antibodies and silicone containing breast implants.

The detection of anti-silicone antibodies in patients with silicone breast implants (SBI) has been undertaken principally in the USA. We undertook a study of 20 women with SBI from different manufacturers from 6 weeks to 20 years after surgery, including those with ruptured implants. They were compared with three control groups: 20 women without implants, 20 women with auto-immune disease and 20 anonymous blood donors. Potential anti-silicone antibodies (IgG) were tested against a variety of silicone polymer antigens using an enzyme linked immunosorbent assay (ELISA) technique which had previously detected positive results in an uncontrolled series. Silicone-free collecting tubes were used. No differences were found between the patients with SBI and controls. However, samples that had been stored for the longest time, or frozen and thawed several times, had the highest levels. These false positives appear to be due to an unknown but human specific IgG binding phenomenon. We conclude that there is no demonstrable anti-silicone antibody formation in these patients with SBI and we would caution that the effect of storage may have been an important factor in previously published assay methods. This study supports the safety of silicone containing breast implants.

Adolescent↗
PubMed2002

Silicone breast implants: correlation between implant ruptures, magnetic resonance spectroscopically estimated silicone presence in the liver, antibody status and clinical symptoms.

OBJECTIVE: To determine the impact of implant integrity on clinical symptoms and antibody status in women with silicone breast implants (SBIs). METHODS: Ninety consecutive women were examined by means of magnetic resonance imaging (MRI) to assess the integrity of their silicone breast implants. The presence of silicone in the liver was estimated by (1)H localized stimulated echo acquisition mode (STEAM) magnetic resonance spectroscopy (MRS). Results were correlated with patients' complaints, as evaluated by a standardized questionnaire, physical examination by a rheumatologist and antibody screening. RESULTS: Breast MRI revealed defects in 24 patients (26.6%); in 13 (54.2%) of these women, silicone was detected in the liver by MRS. Of the 66 patients with MRI-estimated intact implants, 15 (22.7%) had apparent silicone in their liver, arguing for gel bleeding. Clinically, two patients had had rheumatoid arthritis before SBIs, whereas the other patients revealed no typical symptoms of arthritis or connective tissue disease (CTD). The patients with MRS evidence of silicone in the liver had no statistically significant differences in their complaints with the exception of the most frequent symptom, tingling/numbness of the fingers (82.1 vs 51.6%, P=0.006). A positive pattern of antinuclear antibodies (ANA) was obtained in 13 of the 28 MRS-positive patients (46.4%) and in 15 of the 62 MRS-negative patients (24.2%, P=0.033). However, in only one of these 28 ANA-positive patients was a specific weak antibody titre against SS-A detected by ELISA. CONCLUSION: Implant integrity has no major impact on rheumatic symptoms of women with SBIs. This finding supports the standpoint that silicone does not cause either a specific CTD or any other distinct disease entity. However, the moderately increased incidences of ANA-positivity and neuropathy-associated symptoms require explanation.

Adult↗
PubMed1998

Silicon granulomas and dermatomyositis-like changes associated with chronic eyelid edema after silicone breast implant.

Silicone medical products may be associated with various complications. Recent attention has focused particularly on health risks associated with silicone breast implants. The authors present the clinical and histopathological findings in a 71-year-old woman who had previously undergone breast reconstruction with a silicone gel-filled elastomer envelope-type breast implant and who developed severe chronic eyelid edema and inflammation. Extensive systemic evaluation and serologic studies were unrevealing, prompting biopsy of the eyelids. Histopathologic evaluation of the upper eyelids revealed scattered noncaseating granulomas throughout the dermis, an atrophying interface dermatitis with a sparse perivascular lymphocytic infiltrate, and focal perivascular and interstitial lymphocytic infiltrates of the muscles. Scanning electron microscopy demonstrated particles of material within the granulomas, which were revealed by electron probe x-ray microanalysis to contain silicon. The presence of silicon-containing material within areas of eyelid inflammation supports a role for silicon in the pathogenesis of this patient's condition. In the absence of other predisposing conditions, migration of silicone breast implant material must be considered.

Aged↗
PubMed1996

Determining the safety of the silicone envelope: in search of a silicone antibody.

In the controversy surrounding breast implants, one of the crucial questions is whether patients ca form antibodies directed against the silicone shell of the implant. If this were the case, implications for current breast implant development, indeed, for all silicone medical devices, are far-reaching. To evaluate this hypothesis, sera from 18 patients who had tissue expanders and 15 control patients who had no silicone implant exposure were tested retrospectively for antibodies to the silicone using an enzyme-linked immunosorbent assay previously documented as a case report in the literature. Contrary to previous studies, no significant difference in antibody levels was found between test subjects and the controls. Additionally, this enzyme-linked immunosorbent assay for silicone antibodies was poorly reproducible. This study calls into question the existence of specific antibodies to the silicone shell. It also provides further data that the enzyme-linked immunosorbent assay may not be reliable as a silicone antibody test.

Antibodies↗
PubMedDate not supplied

Clinical consequences of the use of highly purified silicone oil. Comparative study of highly and less purified silicone oil.

PURPOSE: To compare the ocular toxicity caused by the use of highly purified silicone oil to less purified silicone oil in humans. METHODS: Fifty-six eyes received 2,000 centistokes (cs) purified silicone oil (group 1) and 42 eyes received 2,000 cs fractionated (highly purified) silicone oil (group 2) after pars plana vitrectormy. Follow-up ranged from 6 to 48 months. RESULTS: Six months after injection, the following complications were found in groups 1 and 2, respectively: ocular hypotension (< 13 mmHg), 39.3% and 31%, sustained ocular hypertension (> 23 mmHg), 19.6% and 19%; acute hypertensive peaks (> 30 mmHg), 23.2% and 11.9%; corneal alterations, 19.6% and 14.3%; emulsification, 1.8% and 2.4%; silicone oil cloudiness, 28.6% and 0%; preretinal reproliferation, 14.3% and 4.8% and total or partial retinal reattachment, 78.6% and 90.5%. CONCLUSIONS: Highly purified silicone oil was better tolerated than the less purified oil and caused fewer complications. Poorly purified silicone oils should be avoided in clinical practice.

Aged↗
PubMed1992

[Silicone molding compounds and latex gloves. The effect of latex gloves on addition and condensation silicones].

Inhibited setting of addition silicones has been observed using latex gloves in the dental office. Therefore four addition silicones as well as four condensation silicones were mixed with seven latex gloves with different properties (sterility, powder, accelerator, inner layer). The masses were mixed with bare hands as a control and--additionally--with powdered hands. Condensation silicones stayed unaffected when put together in exact amounts, while some addition silicones showed nearly complete inhibition. Mixing the condensation silicones under the conditions of daily practice--one spoon of body plus a distinct amount of catalyst-resulted in hardness differences compared to using the exact dose. Nevertheless the resulting impressions were of satisfying quality. The powder-component (Bio-sorb, Surgikos) leads to an accelerated setting. The general dental practitioner/dental hygienist have to consider these aspects while choosing gloves and silicone putties for taking impressions.

Dental Impression Materials↗