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Mechanical energy from intraocular instruments cause emulsification of silicone oil.

AIM: The complications of intraocular silicone oil include emulsification, which may lead to vision-threatening disorders such as keratopathy, secondary glaucoma and retinopathy. The authors study the effect of mechanical energy from surgical instruments on the emulsification of silicone oil. METHODS: Three different handpieces (phacofragmentation, phacoemulsification, high-speed vitrectomy) were placed at the interface of balanced salt solution and silicone oil (1000 and 5000 cst, 200 fluid; Dow Corning). The phacofragmentation handpiece was evaluated over different ultrasound powers and duration. Emulsification was quantified with phase-contrast microscopy and manual counting of digital photographs by a masked examiner. In addition, phacoemulsification was performed in the anterior chamber of a human ex vivo eye with full-fill silicone oil. RESULTS: Emulsification increases with higher phacofragmentation power and duration and is greater for 1000 cst silicone oil. Emulsification of silicone oil occurs with phacoemulsification and high-speed vitrectomy handpieces. CONCLUSIONS: The energy from surgical handpieces is sufficient to result in silicone oil emulsification.

Emulsions↗

Measurement of axial length of eyes with incomplete filling of silicone oil in the vitreous cavity using x ray computed tomography.

AIMS: To establish a reliable method for measuring the axial length of the eye with incomplete filling of silicone oil in the vitreous cavity in order to determine the IOL power before executing combined cataract surgery and silicone oil removal. METHODS: 12 eyes of 12 patients undergoing combined cataract extraction and silicone oil removal between October 1998 and June 2000 were entered prospectively into this study. All eyes were examined using an x ray computed tomography (CT) scanner. Each axial length of a silicone oil injected eye was measured on the best CT slice among eyeball cuts, which showed both the insertions of the medial and lateral rectus muscle, the thickest slice of the lens, and the optic nerve. The IOL power for the eyes was determined using the SRK/T formula based on the CT data. The deviation of postoperative refraction from the goal refraction was evaluated for each eye. RESULTS: The CT slices demonstrated that the vitreous cavity was not completely filled with the oil in all of the silicone oil injected eyes. The deviation of postoperative refraction from the goal refraction was less than 1 dioptre (D) error in six of 12 eyes (50%), and was less than 2 D error in nine eyes (75%). In the other three eyes having more than 2 D error, the axial length was 27 mm or more. CONCLUSION: The CT measurement of axial eye length for determining IOL might be a useful method for evaluating silicone oil injected eyes before combined cataract surgery and silicone oil removal.

Adult↗

Selective MR imaging of silicone with the three-point Dixon technique.

Selective magnetic resonance (MR) imaging of silicone with the three-point Dixon technique was evaluated. This technique, which conventionally allows separation of lipid and water signals, was modified to allow calculation of a silicone-only image and a lipid-water image. Imaging of fat and silicone implant phantoms was performed with a 1.5-T imager and was optimized in vivo in two volunteers who had breast reconstruction or augmentation. Six additional volunteers were then imaged to evaluate selective MR imaging of silicone. With an optimum frequency shift of 105 Hz, a repetition time of 1,000 msec, and an echo time of 28 msec, the modified three-point Dixon technique produced a silicone-only image containing 97.0% +/- 1.0 (standard deviation) of the total silicone signal, 2.6% +/- 0.5 of the fat signal, and 16.6% +/- 6.4 of the water signal. The silicone-fat contrast-to-noise ratio was 47.9 +/- 12.1. This method may be potentially useful in the evaluation of implant-related complications such as rupture.

Breast↗

Autoantibodies and clinical rheumatic complaints in two children of women with silicone gel breast implants.

Considerable interest and efforts are directed at determining the extent to which silicone gel breast implants may contribute to the risk of developing autoimmune disease. There is also comparable interest in determining the extent to which silicone may alter the natural history of an established autoimmune disease. Recently, there has been concern over the possibility that children of women with silicone breast implants might somehow be adversely affected because of either trans-mammary or trans-placental delivery of silicone during either breast feeding or pregnancy. Herein, we describe two children of mothers with silicone breast implants, both female, aged approximately 3 and 9 years, both of whom had long-standing myalgias that were unexplained and did not fit current clinical criteria for juvenile arthritis. Both were found to have positive antinuclear antibodies. Additionally, the 9-year-old girl was found to have a significantly high titer of antibodies against denatured human type II collagen; indeed, her titer was six standard deviations above the mean for normal controls. There have been numerous previous studies which have documented an adverse impact of trace metals, chemicals and some medications on the morphologic and neurologic development of children exposed in utero. Much less information exists on potential toxicity experienced by a neonate through breast feeding, although examples of toxic transmission have been reported. In Western Europe, but not the United States, women with silicone breast implants are advised not to breast feed. Further research should address these concerns and, in particular, women with silicone breast implants, with evidence of leakage or rupture, should refrain from breast feeding until further data are obtained.

Autoantibodies↗

Silicone cream occlusive dressing--a novel noninvasive regimen in the treatment of keloid.

BACKGROUND: The use of silicone oil in the treatment of hypertrophic scars has recently been much discussed. Silicone gel and silicone cream containing 20% silicone oil have been demonstrated to effectively treat hypertrophic scars. However, the results in treating keloid are variable. OBJECTIVE: The purpose of this study was to evaluate the clinical efficacy of silicone cream with occlusive dressing in the treatment of keloid. METHODS: An open study was performed in 15 Chinese patients with single or multiple keloids. Nineteen keloids were randomly selected and treated with silicone cream occlusive dressing (SCOD). The effectiveness was assessed using a scoring system involving elevation, redness, hardness, itching and tenderness or pain of the lesions. RESULTS: Fifteen out of 19 keloids (79%) showed significant improvement after using SCOD for 6 months. None of the keloids progressed. CONCLUSIONS: We conclude that SCOD is easy to apply, noninvasive, painless, almost free of side effects. It is especially useful in children and those who cannot tolerate the pain or inconvenience of other treatment procedures. The action mechanism of SCOD is still unclear, though hydration and occlusion rather than silicone itself may play an important role.

Adult↗

Molecular dynamics study of hypothetical silicon nanotubes using the Tersoff potential.

We have performed classical molecular dynamics simulations for hypothetical silicon nanotubes using the Tersoff potential. Our investigation presented a systematic study about the thermal behavior of hypothetical silicon nanotubes and showed the difficulty in producing silicon nanotubes or graphitelike sheets. However, since the elastic energy per atom to curve the sheet into cylinders for silicon atoms is as low as that for carbon atoms, if graphitelike sheets of silicon are formed, the extra cost to produce the tubes is of a similar order to that in carbon. Through the investigations on the structure and properties of a double-wall silicon nanotube, we concluded that quasi-one-dimensional structures consisting of silicon atoms become nanowires rather than nanotubes in order to minimize the number of sp2 bonds.

Computer Simulation↗

The prevention of pulmonary aspiration with control of tracheal wall pressure using a silicone cuff.

A prospective open randomized controlled study was performed to assess the ability of Euromedical ILM endotracheal tube cuff (silicone cuff) to prevent pulmonary aspiration. The inflation characteristics of this silicone cuff enables the control of tracheal wall pressure. The silicone cuffed tube was shortened and an adjustable flange was used to convert it to a cuffed tracheostomy tube. Twelve patients requiring a tracheostomy on a four-bed intensive care unit (ICU) in a district general hospital received either a silicone or a Shiley cuffed tracheostomy tube. Tracheal wall pressures of both cuffs were maintained at 30 cm H2O with a constant pressure inflation device. Blue food dye was instilled once daily into the subglottic space through a fine catheter above the cuff. There were six patients in the Shiley group and six patients in the silicone cuff group. Dye leaked to the trachea in six (100%) of the Shiley group compared with none (0%) of the silicone cuff group (P = 0.001). This study confirms the effectiveness of this silicone cuff at preventing aspiration and the high incidence of leakage with the conventional high-volume low-pressure tracheostomy tube cuff.

Aged↗

Posterior capsular opacification in pseudophakic eyes with a silicone or acrylic intraocular lens.

PURPOSE: To compare posterior capsular opacification in eyes with IOL of two different materials--silicone or acrylic. METHODS: Eighty consecutive eyes undergoing cataract surgery were prospectively randomized in two groups, 40 eyes receiving a silicone (Sl--30NB) and 40 eyes an acrylic (Acrysof MA60BM) intraocular lens (IOL). The same surgeon performed phacoemulsification and the intraocular lens (PHACO IOL) operation in all cases. Patients were re-examined on the first postoperative day, after one week, four months, and 1-2.4 years. Seven eyes were lost to late control. RESULTS: Clinically significant posterior capsular opacification (PCO) (including eyes with capsulotomy already performed) was equally common in both groups; 25% in the silicone group and 19% in the acrylic group (p=0.53). The posterior capsule remained clear in 61% of the silicone and 76% of the acrylic IOL eyes (p=0.18). In the whole study group, 29% of eyes with and 14% without concurrent ocular diseases had significant PCO (p=0.13). In the silicone IOL group, PCO was more common in eyes with concurrent ocular diseases (44%) than eyes without other diseases (10%) (p=0.049). Eyes with acrylic IOL showed no difference in significant PCO, with or without other diseases (18% and 20%, respectively). CONCLUSIONS: In a consecutive series of 80 cataract eyes central PCO was equally common in eyes receiving a silicone or an acrylic IOL. In the silicone IOL group, however, significant PCO was more common if there was concurrent ocular disease, while with the acrylic IOL concurrent ocular disease did not seem to increase the risk of PCO.

Acrylic Resins↗

Immunohistochemical findings in epiretinal membrane after long-term silicone oil tamponade: case report.

PURPOSE: To report pre- and post-operative macular optical coherence tomography (OCT) and immunohistochemical findings in a case of long-lasting silicone oil tamponade followed by silicone oil removal and epimacular membrane peeling. METHODS: A 69-year-old man with long-standing silicone oil tamponade and an epiretinal membrane at the posterior pole in his right eye (RE) underwent silicone oil/BSS exchange with epiretinal membrane peeling. Preoperatively, RE best-corrected visual acuity was 20/200 and macular OCT examination revealed a small increase in foveal thickness (250 microm) with the appearance of a linear hyper-reflective signal at the foveal vitreoretinal interface and a thicker (440 microm) hyperreflective finding causing posterior shadowing at the vitreoretinal interface inferiorly to the fovea. Histopathologic and immunohistochemical study of the specimen including the epiretinal membrane was performed. RESULTS: Light microscopy revealed extensive rounded empty spaces interpreted as silicone oil bubbles in the preretinal membrane. Macrophages marker (CD68) positive staining cells were found surrounding the empty spaces within the preretinal membrane and several empty spaces were observed intracellularly within macrophage cytoplasm. Thirty days after surgery best-corrected visual acuity was 20/60 and OCT examination showed an evident decrease in foveal thickness (220 microm) with the disappearance of any hyper-reflective signal at the vitreoretinal interface referable to an epiretinal membrane. CONCLUSIONS: The immunohistochemical study showed both silicone oil droplets and macrophagic cells embedded in the epiretinal membrane. Postoperative OCT demonstrated retinal recovery after silicone oil removal and epiretinal membrane peeling, thus justifying an unexpected visual acuity recovery despite the very long term tamponade.

Aged↗

Silicone embolism syndrome: a case report, review of the literature, and comparison with fat embolism syndrome.

Liquid silicone is an inert material that is utilized for cosmetic procedures by physicians as well as illegally by nonmedical personnel. We present a case report and collated clinical findings of 32 other patients who were hospitalized after illegal silicone injections. Symptoms and signs of the "silicone syndrome" included dyspnea, fever, cough, hemoptysis, chest pain, hypoxia, alveolar hemorrhage, and altered consciousness. Bilateral patchy alveolar infiltrates were present on the chest radiographs, and silicone pulmonary emboli were detected in all the patients. The patients could be divided into two groups based on the initial presentation and clinical outcome. Twenty-seven patients in group 1 presented predominantly with respiratory symptoms, and 93% of patients were discharged home within 3 weeks. Six patients (group 2) presented with severe neurologic findings, and experienced rapid deterioration and 100% mortality. The clinical findings after silicone embolism are very similar to the published reports of fat embolism, including hypoxemia in 92% of patients with silicone embolism (patients with fat embolism, 56 to 96%), dyspnea in 88% of patients (patients with fat embolism, 56 to 75%), fever in 70% of patients (patients with fat embolism, 23 to 67%), alveolar hemorrhage in 64% of patients (patients with fat embolism, 66%), neurologic symptoms in 33% of patients (patients with fat embolism, 22 to 86%), petechiae in 18% of patients (patients with fat embolism, 20 to 50%), chest pain in 15% of patients (patients with fat embolism, 26%), and mortality in 24% of patients (patients with fat embolism, 5 to 20%). The similarities among the mode of injury to the lung, the clinical findings, and the high incidence of alveolar hemorrhage suggest a common pathogenesis of silicone and fat embolism syndromes. We discuss the possibility that the activation of the coagulation system may be important in the development of these clinical syndromes.

Adult↗

Silicon's organic pool and biological cycle in moso bamboo community of Wuyishan Biosphere Reserve.

Biomineralization of Si by plants into phytolith formation and precipitation of Si into clays during weathering are two important processes of silicon's biogeochemical cycle. As a silicon-accumulating plant, the widely distributed and woody Phyllostachys heterocycla var. pubescens (moso bamboo) contributes to storing silicon by biomineralization and, thus, prevents eutrophication of nearby waterbodies through silicon's erosion of soil particles.A study on the organic pool and biological cycle of silicon (Si) of the moso bamboo community was conducted in Wuyishan Biosphere Reserve, China. The results showed that: (1) the standing crop of the moso bamboo community was 13355.4 g/m2, of which 53.61%, 45.82% and 0.56% are represented by the aboveground and belowground parts of moso bamboos, and the understory plants, respectively; (2) the annual net primary production of the community was 2887.1 g/(m2 x a), among which the aboveground part, belowground part, litterfalls, and other fractions, accounted for 55.86%, 35.30%, 4.50% and 4.34%, respectively; (3) silicon concentration in stem, branch, leaf, base of stem, root, whip of bamboos, and other plants was 0.15%, 0.79%, 3.10%, 4.40%, 7.32%, 1.52% and 1.01%, respectively; (4) the total Si accumulated in the standing crop of moso bamboo community was 448.91 g/m2, with 99.83% of Si of the total community stored in moso bamboo populations; (5) within moso bamboo community, the annual uptake, retention, and return of Si were 95.75, 68.43, 27.32 g/(m2 x a), respectively; (6) the turnover time of Si, which is the time an average atom of Si remains in the soil before it is recycled into the trees or shrubs, was 16.4 years; (7) the enrichment ratio of Si in the moso bamboo community, which is the ratio of the mean concentration of nutrients in the net primary production to the mean concentration of nutrients in the biomass of a community, was 0.64; and lastly, (8) moso bamboo plants stored about 1.26x10(10) kg of silicon in the organic pool made up by the moso bamboo forests in the subtropical area of China.

Biological Transport↗

Silicone breast implants: pathology.

Questions as to the bioreactivity of silicone breast implants (SBIs) have recently been intensely scrutinized, most notably by the media and legal system. Pathologists must be aware of the controversy and treat each SBI and associated tissue as a potential lawsuit. Grossly, silicone is a clear, viscous substance that may be observed either within or extruding from a silastic bag. By light microscopy, silicone is a nonstainable, nonpolarizable, refractile substance. Thicker sections, especially when viewed by non-Köhler illumination, phase-contrast, and darkfield microscopy will enhance visualization. Ultrastructurally, silicone is an electron-dense, amorphous substance often located within phagocytic vacuoles or extracellularly within the stroma. Correlating electron probe microanalysis allows for reliable identification. In most cases, a fibrous capsule surrounds the SBI, with the interface lining varying from a virtually acellular to a synovial-like lining composed of phagocytic and secretory cells. Silicone can often be identified within the fibrous capsule and also in distant tissues biopsied for suspected autoimmune disorders, such as synovium, skin, and lymph nodes, often without ultrastructural evidence of cytologic effects. This study has demonstrated that silicone accumulates at distant tissue sites due to preexisting inflammation acting as a stimulus. Thus, silicone is not a primary inducer of inflammatory disease processes. These findings are supported by various large epidemiologic studies.

Animals↗

Long-term evaluation of reconstruction of the sellar floor with a silicone plate in transsphenoidal surgery.

OBJECT: The authors have used a silicone plate for reconstruction of the sellar floor during rhinoseptoplastic transsphenoidal surgery because it has greater elasticity and is easier to carve than nasal septal cartilage and sphenoid sinus bone. This study was designed to evaluate the usefulness of this technique based on the authors' experience during the past 7.6 years. METHODS: A silicone plate was used to reconstruct the sellar floor in 69 consecutive patients with sellar tumors that included 60 pituitary adenomas and nine Rathke's cleft cysts. The patients ranged in age from 16 to 82 years (mean 52 years). The postoperative position of the silicone plate could be clearly identified on sagittal or coronal magnetic resonance (MR) imaging as a very low intensity plate (void signal). No displacement or migration of the implanted silicone plate was observed on follow-up MR imaging in any patient. Infections of the lesion such as a pituitary abscess were not observed clinically or radiologically in any patient. Of the 16 patients with intraoperative cerebrospinal fluid (CSF) leakage, only one patient who had a ghost sella developed postoperative CSF rhinorrhea. In all seven patients who underwent repeated surgery for residual or recurrent tumor, the silicone plate that had been placed at the initial procedure was covered with a relatively thin fibrous capsule and the plate was well preserved. The silicone plate was easily removed at reoperation and was useful for detection of the sellar floor window made previously. CONCLUSIONS: These results indicate that a silicone plate can be useful for reconstruction of the sellar floor in rhinoseptoplastic transsphenoidal surgery.

Adenoma↗

Clinicopathologic review of pulmonary silicone embolism with special emphasis on the resultant histologic diversity in the lung--a review of five cases.

It is known that the subcutaneous injection of silicone can lead to severe pulmonary complications, followed in some patients by respiratory failure. Currently, silicone is being increasingly applied in the field of plastic surgery and, unfortunately, the illicit injection of silicone fluid by uncertified practitioners is not uncommon in Korea. We offer a critical pathologic review of 5 cases of pulmonary silicone embolism following illegal injection to the vaginal wall, four of which were fatal and came to legal autopsy. Our findings again confirm that subcutaneously injected silicone can gain access to the pulmonary vascular tree and cause pulmonary embolism. The histologic changes observed in the lung are variable and include four patterns i.e., the mere presence of silicone emboli, congestion and hemorrhage, acute pneumonitis, and diffuse alveolar damage despite the severe critical course in all cases. We were unable to find any histologic pattern that correlates well with the clinical course. Apart from producing emboli in the pulmonary vessels, subcutaneous injection of silicone can obviously cause serious pulmonary disease due to its ability to induce acute to induce acute pneumonitis and even possibly acute respiratory distress syndrome.

Adult↗

Laser-Raman microprobe identification of inclusions in capsules associated with silicone gel breast implants.

Raman spectroscopy (the analysis of scattered photons after excitation with a monochromatic light source) provides a nondestructive method for identifying organic and inorganic materials on the basis of the molecule's characteristic spectrum of vibrational frequencies. Although the technique has been predominantly applied in sciences other than pathology, the recent advent of high-quality microscope optics coupled to optical Raman spectrometers (a variation known as a Raman microprobe) rendered this technique amenable to applications in human pathology. In the Raman microprobe, a laser beam is focused on a spot approximately 1 microm in diameter on the surface of the sample, e.g., tissue, and the scattered light is collected and analyzed. In this investigation, we used the Raman microprobe for the identification of foreign materials in breast implant capsular tissues. The characteristic silicone group frequencies associated with the silicon-oxygen stretch, the silicone-carbon stretch, the silicon-methyl and the methyl carbon-hydrogen stretch frequencies were used to identify polydimethylsiloxane and to define chemical differences among the various other implant-related inclusions. All of the inclusions were positively identified in a series of 44 capsules from silicone gel-filled implants: polydimethylsiloxane was found in 44 of 44 capsules surrounding silicone gel-filled implants; polyurethane was seen in 4 of 4 capsules around polyurethane foam-coated gel-filled implants; 4 of 4 capsules enveloping Dacron patch gel-filled implants revealed Dacron; and talc was identified in 8 of these 44 capsules. Raman microspectroscopy provides a rapid, accurate, and sensitive method for identifying inclusions associated with silicone and other implant materials in tissue.

Breast↗

[The best timing of silicone oil removal].

OBJECTIVE: The study was designed to approach the best timing of silicone oil removal after its injection into the vitreous cavity in vitrectomy for reattachment of retinal detachment. METHODS: The silicone removal was performed on 100 eyes of 96 patients, and the incidence of silicone complications was analyzed statistically. RESULTS: The complication incidence increased with the time of silicone oil removal delayed. There are statistically significant differences in the complication incidence not only between the group with silicone oil removal within 3 months and the group with the removal later than 5 months, but also between the group with the removal within 5 months and the group with the removal later than 5 months. The complication incidence was 100% in the group in which the silicone oil was removed later than 18 months after its injection. CONCLUSIONS: The silicone oil should be removed no longer than 6 months after its injection, and the best timing to remove the oil is 2 to 3 months.

Humans↗

Neodymium:YAG capsulotomy rates following phacoemulsification with implantation of PMMA, silicone, and acrylic intraocular lenses.

BACKGROUND AND OBJECTIVE: Posterior capsular opacification (PCO) is the most common visually disabling sequela of modern cataract surgery. Methods of reducing its incidence include the development of newer surgical techniques and intraocular lens (IOL) materials and designs. The aim of this study was to compare the incidence and time interval of development of PCO, and the requirement of laser capsulotomy in patients implanted with a polymethylmethacrylate (PMMA), silicone, or acrylic IOL. PATIENTS AND METHODS: The data of 340 consecutive patients who underwent phacoemulsification and implantation ofa PMMA, silicone, or acrylic intraocular lens were analyzed. The aim of this study was to compare the incidence and time interval of development of PCO, and the requirement of laser capsulotomy in patients implanted with a PMMA, silicone, or acrylic IOL. RESULTS: The incidence of PCO was found to be significantly less in the acrylic group (6.5% as compared to 21.74% and 26.6% in the PMMA and silicone groups, respectively; P = 0.01297 and 0.0039). Most patients (65%) exhibiting PCO in the PMMA group developed it within the first six months. In the silicone group, development of PCO was delayed. In 60% of patients, it appeared 18 months after surgery. Neodymium:YAG capsulotomy was required in 45% and 60% of patients developing PCO in the PMMA and silicone groups, respectively, while it was required in only 1 of the 4 patients developing PCO in the acrylic group. CONCLUSION: This study indicates that implantation of an acrylic IOL helps reduce the incidence of PCO as well as the need for Nd:YAG capsulotomy. PMMA IOLs require Nd:YAG capsulotomy earlier in the postoperative period as compared to silicone IOLs.

Acrylic Resins↗

[Biodegradation of silicone in voice prosthesis].

The most important problem of the useful life of vocal prostheses is bacterial and especially mycotic colonization of their surface which impaired tightness of the closing valve of the prosthesis and caused subsequent leakage of fluids and food into the airways. The objective of the present study was to prevent colonization of the silicone surface and to prolong the service life of the prosthesis. The implanted prostheses were examined under microscope after varying intervals in vivo. The silicone of the implanted prosthesis was colonized by numerous microorganisms, in particular moulds. Seventeen bacterial and mycotic strains were identified. They behave to Candida, Acinetobacter, Micrococcus, Pseudomonas, Bacillus and Chryseomonas. The results confirmed the deep degradation of silicone rubber located in islets. Plant of bacterial tissue were inoculated on two types of silicone disks. Two types of silicone were tested (Silastic Q7-4550-50ShA and Q7-4765-65) after 4, 8 and 12-week exposure. Neither of these materials was attacked by mycotic agents in vitro. Only frame print was appreciable in five hundred times magnification. The second object of the study was to recognize the main degradation factor that means a kind of microorganism. The ability of microorganisms to assimilate oligo- and polyorganosiloxans was studied. Candida albicans does not seem like a typical microorganism assimilating silicon rubber. The results of our study proved Microccus as a typical vector which assimilates silicone.

Bacteria↗