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PubMed1992

Renal handling of silicon in normals and patients with renal insufficiency.

We have compared the renal handling of silicon in 16 patients with renal insufficiency to 14 normal individuals. Silicon, phosphate and creatinine were measured in plasma and urine samples. The renal insufficiency group showed significant increases in plasma silicon (1.28 +/- 0.19 vs. 0.17 +/- 0.03 mg/liter), creatinine (5.19 +/- 0.85 vs. 0.89 +/- 0.03 mg/dl) and phosphate (1.33 +2- 0.11 vs. 1.07 +/- 0.4 mmol/liter). Fractional phosphate excretion was increased in the renal insufficiency group (0.55 +/- 0.07 vs. 0.14 +/- 0.01). In contrast, the fractional excretion of ultrafiltrable silicon was not significantly different between groups (0.78 +/- 0.07 vs. 0.87 +/- 0.06). It is concluded that renal insufficiency does not alter the tubular handling of silicon and that regulatory control of silicon excretion is unlikely.

Creatinine↗
PubMed2000

Permanent tunneled silicone central venous catheters for autologous PBPC harvest in children and young adults.

Children with high risk malignancies are usually given permanent (Hickman-type) tunneled silicone rubber central venous catheters (silicone CVCs) for the administration of chemotherapy. In the past, these children received an additional short-term polyurethane dialysis CVC for stem cell apheresis. To avoid placement of an additional short-term CVC, we started in 1995 to use pre-existing silicone CVCs for PBPC harvests. From May 1996 to February 1999 we evaluated 165 harvests in 37 children and 14 young adults (16-28 years) treated with high-dose chemotherapy and stem cell support, comparing CD34+ cell harvest efficiency, catheter tolerability, and complications in three different approaches to vascular access. Pre-existing silicone CVCs (64%) or peripheral venous cannulae (15%) were the first choice for venous access. Only when these failed were polyurethane CVCs (21%) used. No significant difference was seen between these three groups, even after dividing the silicone CVC group (105 harvests in 32 patients) into three subgroups according to weight and age. The most frequent problems were citrate toxicity (n = 33), mechanical obstruction inside (n = 9) and outside the cell separator (n = 2), decreased draw line flow in silicone CVCs (n = 7), decreased draw line flow in peripheral venous cannulae (n = 6), and one occlusion in a polyurethane CVC. Pre-existing CVCs and peripheral venous cannulae functioned efficiently when used as a draw line in 79% of the apheresis procedures without significantly reducing single harvest efficiency or catheter tolerability. Consequently, the risks and costs associated with the placement of a dialysis CVC could be avoided in the majority of cases. Bone Marrow Transplantation (2000) 26, 781-786.

Adolescent↗
PubMed2006

Reliability of the IOLMaster in axial length evaluation in silicone oil-filled eyes.

PURPOSE: To assess the reliability of IOLMaster in axial length (AL) measurement in phakic silicone oil-filled vs pseudophakic saline-filled eyes. METHODS: Ten eyes of 10 patients, vitrectomized with silicone oil tamponade and scleral buckled with significant lens opacity were enrolled. Optical biometry with IOLMaster (Carl Zeiss Meditec AG, Germany) was performed 1 day before and 1 week after silicone oil removal and phacoemulsification with artificial intraocular lens (IOL) implantation in order to assess changes in AL measurements. RESULTS: Mean AL was 26.16+/-1.23 mm (range 24.64-28.8 mm) and 26.27+/-1.46 mm (range 25.26-29.6 mm), respectively, the day before and 1 week after silicone oil removal and cataract surgery, and the difference was not statistically significant (P=0.2). CONCLUSIONS: Presence vs absence of silicone oil tamponade as well as phakic vs pseudophakic status in buckled and vitrectomized eyes did not influence the AL measurement by means of no-contact optical biometry, suggesting that such eyes might be candidate for silicone oil removal and cataract surgery at one time.

Aged↗
PubMed2001

Silicone versus nonsilicone gel dressings: a controlled trial.

BACKGROUND: Silicone gel dressings decrease scar volume and soften hypertrophic tissue, allowing it to be more easily controlled by other methods. Although silicone does not appear to be an essential component of the treatment, nonsilicone dressings have been reported to cause no change in physical parameters during a 2-month treatment period. OBJECTIVE: To compare silicone and nonsilicone gel dressings in the treatment of keloids and hypertrophic scars, including a control group, and to evaluate the effectiveness of these treatments using two new assessment techniques. METHODS: Patients were randomly chosen to receive silicone or nonsilicone gel dressings in a 4.5-month controlled prospective study. Scar size, induration, and symptoms were evaluated before and after the treatment. Scar color was visually measured using a color palette catalog, and a new device was developed to measure intracicatricial pressure. RESULTS: All of the measured parameters were significantly reduced in both silicone- and nonsilicone-treated groups, as compared to the control, with no significant differences between them. CONCLUSION: Silicone and nonsilicone gel dressings are equally effective in the treatment of keloids and hypertrophic scars.

Adolescent↗
PubMed2003

Lip silicone granulomatous foreign body reaction treated with aldara (imiquimod 5%).

We report a case of a lip granulomatous reaction after injection of silicone being treated successfully with topical Aldara (Imiquimod 5%). Silicone granulomas and the inflammatory foreign body reaction that can occur are some of the complications that arise from using silicone for cosmetic enhancement. The inflammatory reaction of this patient first appeared shortly after silicone injection of both the upper and lower lips. Histopathologic examination revealed a foreign body inflammatory reaction that is consistent with silicone granuloma. Although this reaction has been described extensively in the dermatologic literature as one of the disfiguring side effects of silicone injection, its treatment has plagued cosmetic dermatologists. We report the use of an immunomodulatory cream Aldara (Imiquimod 5%) to treat this type of reaction.

Adjuvants, Immunologic↗
PubMed1998

Roller pump induced tubing wear of polyvinylchloride and silicone rubber tubing: phase contrast and scanning electron microscopic studies.

Tubing wear and spallation have long been recognized as complications of roller pumps used in cardiopulmonary bypass (CPB) although the reported results of studies of polyvinylchloride (PVC) and silicone rubber tubing wear are still controversial. We conducted phase-contrast microscope (PCM) and scanning electron microscope (SEM) studies of roller pump induced tubing wear. A closed CPB circuit was constructed, and both PVC and silicone rubber tubing (1/2 inch internal diameter [ID]) were tested under normal and tight occlusions of a dual roller pump at a typical CPB flow rate (4,500 ml/min) for 1, 2, 4, and 6 h in quintet. After each pump run, the tubing was removed. It was first examined with PCM, and suspicious portions were then analyzed in detail using SEM. In silicone rubber tubing of longer running time, the external diameter often decreased. Wear was invariably found on the luminal surfaces at the junction of the inner and outer walls of both the PVC and silicone rubber tubing with no significant differences between normal and tight occlusion. The grooves in the PVC tubing were narrow and continuous with occasional deep cracks in the tubing after more than 3 h of pump run. The grooves in the silicone rubber tubing were wide and often interrupted with occasional V-shaped elevated areas. Craters of less than 50 microns occurred sporadically in both types of tubing. Neither PVC nor silicone rubber tubing offers advantages in terms of roller pump induced tubing wear and spallation.

Cardiopulmonary Bypass↗
PubMed2004

[Biocompatibilty of silicon nitride ceramic in vitro. A comparative fluorescence-microscopic and scanning electron-microscopic study].

BACKGROUND: With regard to its favorable physical properties, silicon nitride ceramic is considered as biomaterial for human medical application. Minor controversy exists about the biocompatibility of the material. METHODS: Cytotoxicity testing, cell viability and morphology assessment was performed applying the L929-mice fibroblast cell culture model in a direct contact assay. Testing materials were silicon nitride ceramics of different surface properties and titanium alloy as a reference. Polyvinylchloride served as a negative control. The cells were stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy. Scanning electron microscopy was applied to additionally investigate cell morphology. RESULTS: No cytotoxic effects were observed on the silicon nitride ceramic samples; moreover cell morphology remained the same as on titanium. Avital cells were present exclusively on PVC. The cell growth in the silicon nitride samples showed no significant differences compared to titanium. Cell counts on all polished surfaces showed significantly higher numbers. Scanning electron microscopy revealed typical fibroblast morphology with filiform extensions. CONCLUSION: The current results indicate a favorable biocompatibility of silicon nitride ceramic. Cell growth, viability and morphology are comparable to parameters of titanium. Polished surfaces appear to promote cell growth. Further in vivo studies are mandatory prior to human medical application. Owing to its favorable physiochemical properties, especially its superior resistance to mechanical stress, silicon nitride could serve as a biomaterial for osteosynthesis of bone with mucosal attachment.

Alloys↗
PubMed1995

[Endonasal implantation of a silicon mold improves the long-term outcome of revision surgery in lacrimal duct stenoses].

BACKGROUND: Uncomplicated dacryocystorhinostomy after dacryocystitis with lacrimal sac obstruction has a success rate of 85%. However therapy of restenosis poses a problem. Vast destruction of lacrimal and nasal mucosa renders the drainage system susceptible for further stenosis. This article presents a new surgical procedure for the treatment of restenosis of the nasolacrimal apparatus. The major difference from other techniques is the endonasal implantation of a silicon foil. This counters the development of synechiae and promotes the epitheliasation of wound surfaces. As a result the nasal mucosa can easier gain access to lacrimal mucosa. A complete mucosal coating of the reconstructed lacrimal drainage system is an important condition for the sufficient drainage of the tear-film. PATIENTS AND METHODS: In 30 patients with restenosis after one or multiple dacryocystorhinostomies a silicon foil was implanted endonasally as part of their surgical revision. After skin incision and removal of scar tissue the bony ostium was enlarged. The canaliculi were intubated with silastic tubing. Afterwards the endonasal synechiae were split and a 0.2-0.4 mm silicon foil was implanted endonasally und fixed. The silastic tubing was brought through a hole in the silicon foil and knotted inside the nose. Then the wound was closed. Postoperative evaluation of the surgical success ranged from 3 to 36 months (mean 16 months). RESULTS: The postoperative result was good in 24 patients. Sixteen patients were without symptoms. 8 had epiphora only on stress. The latter felt their situation to be greatly improved. The long-term results were directly proportional to the amount of reconstructable mucosa and inversely proportional to the severity of canaliculus damage. Adverse reaction to the silicon foil were not noted. CONCLUSION: Endonasal implantation of a silicon foil is a new, easy and successful technique for the treatment of endonasal synechiae and restenosis of the nasolacrimal apparatus.

Adolescent↗
PubMed1992

[Therapeutic possibilities in lens opacity after silicon oil tamponade].

The most important complication of intraocular silicone oil is cataract formation. This leads not only to deterioration of the patients vision, but also to impairment of fundus visualisation. Preventing cataract formation by removing the silicone oil in the first postoperative weeks is hampered by an increased risk of redetachment. Furthermore, even with silicone oil vitreoretinal complications occur in up to 37%. Therefore if cataract surgery becomes necessary, it should be performed maintaining the silicone oil tamponade. The most suitable technique under this condition is phacoemulsification, avoiding damage to the posterior capsule and zonules. Due to this consideration we performed phacoemulsification with in the bag implantation of intraocular lenses in 13 eyes after silicone oil procedure. In no case intra- or postoperatively silicone oil was visible in the anterior chamber. Visual acuity improved in about 50% of the eyes despite of capsular fibrosis being present in all cases. Postoperatively YAG-lasercapsulotomy led to functional improvement in only one out of three eyes.

Adolescent↗
PubMed1984

[Echographic findings following intravitreous silicone injections].

In 27 patients treated by silicone injection combined with pars plana vitrectomy various conditions of the retina were demonstrated by echography. As a result of silicone oil instillation the vitreous distance is prolonged and the sound absorption is higher. At the border of the silicone bubble the reflective echos are especially high. From the form of the border echos of the silicone bubble it is possible to determine whether there is a retinal detachment, with or without subretinal silicone. It is shown that the examination results always depend on the position of the patient's head when the silicone bubble does not completely fill the vitreous cavity. The authors have worked out a set of rules which, because of their reproducibility, enable the surgeon to draw diagnostic conclusions in cases of opacity of the anterior segment.

Humans↗
PubMed2005

Effect of storage duration on tensile bond strength of acrylic or silicone-based soft denture liners to a processed denture base polymer.

OBJECTIVE: To investigate the effect of storage duration on the tensile bond strength of acrylic and silicone-based denture base materials with liners either heat-cured or auto-cured. MATERIAL AND METHODS: The denture liners investigated were Vertex soft (acrylic-based, heat-cured), Coe soft (acrylic-based, auto-cured), Molloplast-B (silicone-based, heat-cured), and Mollosil plus (silicone-based, auto-cured). The soft liner specimens were 10 x 10 x 3 mm and were processed between two PMMA blocks. They were tested following immersion in water at 37 degrees C for 1 day, 1 week, and 1, 3, and 6 months. Tensile bond strength was measured using a universal testing machine (Testometric Micro 500) at a crosshead speed of 20 mm/min (n = 10 specimens per experimental group). Multiple ANOVA and Tukey HSD were used to analyse the data at a pre-set alpha of 0.05. RESULTS: The results indicate that the tensile bond strength of acrylic-based soft liners is greater than that of silicone-based materials. The bond strength of all lining materials decreases with storage duration; the decrease being greatest for the acrylic-based soft liners. The decrease in bond strength of the auto-cured materials is greater than that of the heat-cured products. CLINICAL SIGNIFICANCE: Comparison of the materials in this study indicates that the silicone-based, heat-cured soft liner is superior, based on the tensile bond strength property. Use of silicone-based, heat-cured soft liners may provide better clinical success over a long period. These laboratory results need to be verified by clinical testing.

Acrylic Resins↗
PubMed1959

The metabolism of silicon in the rat and its relation to the formation of artificial siliceous calculi.

The urinary excretion of silicon in the rat was found to be enhanced beyond normal levels by the administration of various chemical forms of silicon. The excretion was enhanced to a much greater degree by the administration of ethyl silicate than by magnesium trisilicate, sodium metasilicate, or water glass. The tolerance level of rats to sustained daily doses of ethyl silicate fed via stomach tube was approximately 15 to 30 mg. of silicon per rat per day. Urinary silicon excretion was found to be a straight line function of the concentration of ethyl silicate administered, via stomach tube, with approximately 18 per cent of the administered silicon appearing in the urine at all levels tested. Using sustained dietary additions of ethyl silicate as a means of enhancing urine silicon levels, artificial siliceous urinary calculi were consistently produced on zinc pellets implanted in the bladders of rats.

Animals↗
PubMed1999

Neutrophil chemotaxis on silicone and polyurethane surfaces.

Silicone vascular catheters have a greater risk of infection and produce greater inflammation in vivo and greater complement activation in vitro than other vascular catheter polymer materials. This study investigated whether polymorphonuclear leukocyte (PMNL) chemotaxis under agarose on silicone surfaces is different than on polyurethane (PU). Glass slides were coated with silicone and PU by use of a constant-speed dipping apparatus. Chemotaxis (3 h) in response to (10-7 mL) FMLP, zymosan-activated serum, and fresh serum (100%) was greater on silicone than on PU (P<.05). Polyclonal antibody to C5a blocked >50% of the movement toward serum (P<.05). Serum in the PMNL well significantly decreased chemotaxis toward FMLP on silicone (P<.05) but not on PU. These findings suggest that excessive complement activation by silicone may interfere with chemotaxis, but further work is necessary to determine whether this is relevant to an increased risk of catheter-related infection.

Blood↗
PubMed1980

Biochemical and morphological changes associated with long bone abnormalities in silicon deficiency.

The purpose of this paper was to investigate long bone changes in silicon deficiency more extensively and under a new set of conditions. Long bone abnormalities have been produced in silicon-deficient chicks fed a casein-based rather than amino acid-based diet and under an entirely new set of conditions. As demonstrated previously feeding amino acid diets, the long bones of cockerels fed a silicon-supplemented basal diet and sacrificed at 4 weeks had a significantly greater amount of articular cartilage and water content as compared with the silicon-deficient group. Biochemical analyses of tibia for bone mineral, non-collagenous protein, hexosamine and collagen demonstrated that tibia from supplemented chicks had a significantly greater percentage and total amount of hexosamine and greater percentage of collagen than deficient chicks, the difference being greater for hexosamines than collagen. Tibia from silicon-deficient chicks also showed marked lesions, profound changes being demonstrated in epiphyseal cartilage, especially striking in the proliferative zone. The disturbed epiphyseal cartilage sequences resulted in defective endochondral bone growth indicating that silicon is involved in the metabolic chain of events required for the normal growth of bone.

Animals↗
PubMed1992

Silicone breast implants and immune disease.

Silicone was originally regarded as inert in the human body. Silicone medical devices have been associated with various complications that may involve an immune reaction to silicone or a silicone organic complex. There have been more than 80 cases reported in the medical literature of a varied systemic autoimmune illness in patients who have had various foreign materials placed in the breast. Controversy exists as to which complications have a cause and effect relationship, and which represent coincidental findings. It is difficult to distinguish between nonspecific local reactions and reactions that have an immunological basis. Approximately 1,000,000 to 2,000,000 women in the United States have had silicone breast implants inserted for reconstruction or augmentation mammaplasty; 28 of those patients have been reported to have developed a systemic autoimmune disease. Data on the 28 reported cases do not in any way prove a causal relationship between breast implants and immune disease. Given the natural incidence of autoimmune diseases, we would expect a coincidental occurrence in the United States of more than 1,000 cases of autoimmune disease in women who had undergone breast implant surgery. Additional information must be obtained to resolve the question. The true incidence of autoimmune disease in patients with implants needs to be determined. A prospective registry of implant patients should be established and comprehensive retrospective information obtained on the implant patient population. Further experimental work is necessary on the bioreactivity of silicone. Patients with implants and autoimmune disease, once identified, must be carefully evaluated by physicians who are experienced in the treatment of autoimmune disease.

Autoimmune Diseases↗
PubMed1995

Evaluation of silicone-gel sheeting on early wound healing of linear incisions.

Topical silicone-gel sheeting has been shown to be beneficial in the treatment of established hypertrophic and keloid scars. Certain individuals and incisions in specific body sites appear to be at increased risk for the development of such scars. A simple, inexpensive, and preventive treatment in these individuals at increased risk could potentially minimize the extended period of pressure therapy and repeated steroid injections that are often required to optimize outcome. However, the effects of applying silicone-gel sheeting in the immediate postoperative period as a preventive measure have not been investigated to date. Because silicone-gel sheeting influences the remodeling and maturation phase of collagen formation, we believed it prudent to determine whether silicone-gel sheeting had any deleterious effect on early wound healing, as demonstrated by in vivo biomechanical testing of wound strength and histological assessment. To investigate the potential effects of silicone-gel sheeting on acute wound healing and its possible application for prevention of hypertrophic scars, a study was designed in the hairless guinea pig. In phase 1 of the study, bilateral dorsolateral incisions were made, allowing each guinea pig to serve as its own control. One wound was dressed with silicone-gel sheeting, and the control site was dressed with Nu-gauze dressing. Wounds were then assessed visually and with in vivo biomechanical analysis of wound strength at days 3, 5, and 7 postoperatively (n = 7 per group). Phase 2 of the study compared identical dressings in a similar animal model using a single dorsal midline incision, in which alternate halves of each wound served as the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Monitoring the axilla in patients with silicone gel implants.

Migration of silicone beyond the breast implant capsule may occur as a result of silicone bleed, leak, or rupture, and it may indicate failure of implant envelope integrity. We report a series of 23 patients with silicone implants who had axillary lymph node biopsies for palpable masses. Group 1 (n = 15) had biopsies performed an average of 6 years following aesthetic augmentation, and Group 2 (n = 8) had biopsies performed an average of 5 years after mastectomy reconstruction. All biopsies demonstrated foreign body reaction consistent with silicone migration. Five patients in Group 1 and two in Group 2 also had breast cancer detected by the axillary biopsy. Evaluation of the axilla utilized a combination of one or more techniques, including mammography, ultrasonography, magnetic resonance imaging, and fine-needle aspiration. We conclude that (1) routine evaluation of the axilla is mandatory in all patients with silicone breast implants; (2) an algorithmic approach in diagnosing axillary masses may be helpful, especially in augmentation patients; and (3) axillary masses detected by clinical examination or other means must be biopsied, even in the face of negative screening studies, because breast cancer may be coincidental with a silicone granuloma.

Adult↗
PubMed2002

Silicone gel breast implant failure: evaluation of properties of shells and gels for explanted prostheses and meta-analysis of literature rupture data.

After 30 years of clinical use, the 1992 Food and Drug Administration moratorium on silicone gel breast implants (SGBIs) resulted from a paucity of scientific data concerning their safety. The frequency of rupture and reoperative procedures was not known, nor were reliable data available for changes in the physical properties of shells and the composition of gels that might lead to SGBI failure. For this reason the authors conducted large-cohort meta-analyses of failure data for SGBIs based on numerous literature reports and also investigated systematically shell and gel properties from explanted SGBIs. They report their failure analysis data for more than 9,770 SGBIs (an update of an earlier study of more than 8,000 implants) as well an examination of the properties of shells and gels for 74 explanted SGBIs that ranged in age from 2 to 19 years (mean implanted age, 9.9 years). The explants tested were from several different manufacturers. For the modest-size explant cohort that was tested, 31 of 74 implants (42%) were found to be ruptured (some extensively). Even many intact shells were so weakened that only 51 shells had sufficient strength to enable preparation of samples for testing of mechanical properties and for analysis of composition by solvent extraction. Shells were found to contain 15 to 25% of extractable silicone. Exhaustive extraction of gels showed that they actually contained very little crosslinked silicone--85 to 95% being extractable soluble silicone fluid. Tensile and tear strengths of explanted silicone elastomer shells were lower than unimplanted prostheses and were generally well below reported manufacturers' values. This updated large-cohort failure analysis continues to show that shell rupture is related directly to implant duration (e.g., from analysis of variance statistics, 26% failure at 3.9 years, 47% at 10.3 years, 69% at 17.8 years; < or = 0.001). However, for the relatively small series of explants for which physical property data are reported, no significant correlation was observed between implant duration and the degradation of implant strength. It therefore appears most reasonable to conclude that after early weakening of shells as a result of swelling of the shell elastomer by diffusion of silicone oil from the gel, SGBI failure can occur in a time-dependent manner as a result of continuing implant motion and cyclic stresses that are exacerbated by stress concentration at thin areas, defects, and folds in the shells.

Breast Implants↗