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At least 1,135 records · Page 63Linked to original sources
PubMed1992

Silicone oil in the management of giant retinal tears.

To evaluate the results of using and removing silicone oil in the management of giant retinal tears, 24 cases of vitrectomy with fluid-silicone oil exchange were reviewed. We did not use cryotherapy in any case. For chorioretinal adherence, we used either endolaser or postoperative external laser and a narrow buckle. The retina was reattached successfully in 22 (91.6%) of the 24 eyes. Of these, visual acuity was 20/200 or better in 18 (75%) eyes. This was significantly better than the preoperative visual acuity (P = .02). After removing the silicone oil in 15 cases, 13 (92.8%) had visual acuities of 20/200 or better, which was considerably better than that of the group in which the silicone oil was not removed (P = .006). We recommend removing the silicone oil and additional peeling of membranes an average of six months postoperatively when the eye is stable.

Adolescent↗
PubMed1992

The biophysical and histologic properties of capsules formed by smooth and textured silicone implants in the rabbit.

Capsular contracture remains the major complication of reconstructive and aesthetic breast surgery. The purpose of this investigation was to determine if a silicone implant with a textured surface will form a capsule of significantly different biophysical and histologic properties than conventional smooth silicone. Thirty smooth and 30 textured silicone tissue expanders were implanted under the panniculus carnosus of rabbits. After 3 months, measurements related to contracture were performed on anesthetized animals in an investigator-blinded, controlled manner. Intraexpander pressures were measured as saline was injected over time. We found a significant correlation between intraexpander pressures, applanation tonometry, and Baker class. Histology revealed a thicker, more adherent, and inflammatory capsule around the textured silicone implants as compared with the smooth silicone implants. Dynamic pressures were plotted against volume of saline within the two types of implants. Statistical analysis revealed that the textured implants form a tighter and thicker capsule than the smooth implants after 3 months of observation (p less than 0.005).

Animals↗
PubMed2005

Selective protein adsorption on micro-textured P-type and N-type silicon wafers.

There has recently been a great deal of effort put towards the development of bioMEMS-based electrochemical biosensors for use in implantable devices. Currently, the primary issue limiting the lifespan of implantable sensors is protein and cell adhesion (biofouling) to the sensor surface, which impedes the sensor's access to analyte. To better understand this problem, it would be useful to have an understanding of how silicon-based microdevices interact with proteins in a physiological environment. To help answer this question, we investigated the interactions of proteins with microtextured silicon wafers. Bulk micromachining techniques were used to create micro-textures that varied between 5 and 80 microns in size nd spacing. We used n-type and p-type silicon wafers with a <100> crystal orientation. Shapes such as rectangles, circles, and triangles were fabricated that were recessed into the silicon substrate. The features were estimated to be between 3 and 8 microns in depth. After the features were created, the wafers were coated with a layer of silicon dioxide. Once fabrication was complete, the wafers were incubated in vitro ith fluorescently tagged Albumin (500 microg/ml in Phosphate-Buffered Saline, PBS) for 5 minutes. The wafers were then rinsed with PBS solution and viewed using an epifluorescence microscope. Albumin adsorbed selectively onto the micropatterned wafers. Depending on the type of wafer we found that albumin adsorbed selectively onto either the bulk surface, the sidewalls, or the bottom of the etched feature.

Adsorption↗
PubMed2005

Silicone sealers, acetic acid vapours and dental erosion: a work-related risk?

The aim of the present study was to investigate whether the acetic acid released by some silicone sealers during the curing process poses an increased risk for dental erosion, thus constituting an occupational hazard to exposed individuals. The material comprised 13 individuals (x=30 years, 10 men and 3 women) who had been exposed to an average of 4.2 years' (range 0.6-10 years) of working with silicone. Each had comprehensive medical and dental examinations carried out. A sex- and aged-matched group of 20 healthy, unexposed workers from the same company served as controls for the medical examination, while study models from randomly selected sex- and age-matched individuals were used as controls for assessing the severity of erosion. Using a questionnaire, an assessment of the role of various possible factors related to oral and general health, and to dental erosion in particular, was made for each participant in the exposed group. Clinical examination included recordings of severity of dental erosion, presence of "cuppings", DMFT, salivary secretion rate and buffer capacity, visible plaque index and gingival bleeding index. In addition, bitewing radiographs, study casts and intraoral colour transparencies were obtained for each individual. The severity of dental erosion was significantly higher in those exposed to silicone compared to controls. There was also a significant correlation between the period of exposure to silicone in the workplace and severity of erosion. Medical problems, especially with regard to upper respiratory tract symptoms, were significantly more common among exposed individuals than controls. In conclusion, a relationship between occupational exposure to acetic acid vapours from silicone sealers and development of dental erosion would appear to exist.

Acetic Acid↗
PubMed2005

[Effect of silicon and latex urinary catheters: a comparative study].

OBJECTIVE: To evaluate the effect of silicon and latex urinary catheters on urinary mucosa. METHODS: A randomized, controlled prospective clinical trial was carried out in 60 patients admitted in the Department of Neurosurgery, who required long-term use of an indwelling urinary catheter. The patients were divided into 2 equal groups with placement of silicon or latex urinary catheter, and routine laboratory urine test was performed on a regular basis and the patients feelings during catheter retention were recorded. RESULTS: Patients with placement of indwelling silicone catheters reported no obvious discomfort in relation to the catheter placement and had significantly lower incidence of hematuria identified microscopically than those with common latex catheters. CONCLUSION: Compared with latex catheters, silicone catheters cause less injuries and reduce substantially irritation of the urinary mucosa, and we suggest the use of silicone catheter in patients requiring long-term indwelling urinary catheters.

Adult↗
PubMed2005

Effect of intraocular silicone oil on ocular tissue.

The aim of this study was to find out to which extent the instilled silicone oil affects the changes of lens, cornea, and the ocular pressure with regard to its time kept in the operated eye with a lens. The study was carried out on the sample of 40 patients, divided in three groups. The first group of patients with the silicone oil kept in the eye during 3 months, the second one during 3-6 months, and the third one during 6-9 months. Statistically important changes were observed in the progression of the lens opacification with the patients, progressively with the time of keeping the silicone oil in the eye. The followed cornea opacifications and increased ocular pressure were not statistically significantly linked with the length of keeping the silicone oil in the eye, so that it can be concluded that the silicone oil is the best substitute for the vitreous body but it should be removed from the eye, most frequently, in the period of 3-6 months from the date of its instillation, and after 3 weeks at the earliest.

Cornea↗
PubMed2006

[Expression and role of nuclear transcription factor Sp1 in macrophages stimulated by silicon dioxide].

OBJECTIVE: To study the expression and localization of nuclear transcription factor Sp1 in macrophages after stimulated by silicon dioxide in vivo and in vitro. METHODS: Forty Sprague Dawley rats were randomly divided into the control group and the silica exposure group, 20 in each group. The rat silicosis models were established by direct tracheal instillation of silica into rat lung (0.2 g/kg) only once while the control group was instilled with equal amount of saline. Animals were killed at 1st, 7th, 14th, 21st and 28th day after instillation. Dynamic changes of Sp1 protein expression and its cellular localization were detected by immunohistochemistry in pulmonary macrophages. In vitro, Sp1 mRNA and protein expression and their dynamic changes were monitored by RT-PCR and western blotting after stimulated by silicon dioxide in cultured RAW264.7 macrophages respectively. Cellular localization of Sp1 protein was characterized by immunocytochemistry. RESULTS: Compared to the control group, the Sp1 protein expression was increased in pulmonary macrophages and reached the peak at the 14th day in the silica exposure group. In vitro, the Sp1 mRNA level began to rise at 30 minutes after the administration of silicon dioxide and reached the peak at 240 minutes and then decreased to the minimal level at 960 minutes. The Sp1 total protein and nuclear protein also exhibited the similar trend. The former reached the peak at 240 minutes and the latter at 480 minutes. The significant nuclear translocation of Sp1 protein was observed at 120 minutes after the administration of silicon dioxide and became most significant at 480 minutes. CONCLUSION: Silicon dioxide can activate nuclear transcription factor Sp1 in macrophages in vivo and in vitro. Sp1 might play an important pathogenic role in the development of silicosis.

Animals↗
PubMed2006

[Silicon application enhances resistance to sheath blight (Rhizoctonia solani) in rice].

The enhancing resistance and decreasing incidence to sheath blight (Rhizoctonia solani) by silicon were studied from cytological and physiological aspects by using rice plants solution-cultured with silicon supplementation or with silicon-deficiency. By an environmental scanning electron coupled with X-ray microanalysis, as well as gravimetric quantification, the number of siliceous cell and Si content of the Si(+) rice leaf were much more than those of Si(-) rice leaf (Figs.1,2; Table 1). After being inoculated with R. solani MDA content in Si(+) rice plants was almost higher than that in Si(-) rice plants, SOD activity in Si(+) rice plants was always higher than that in Si(-) rice plants, SOD activity in Si(+) rice plants reached a minimum on 4 d, and POD activity was at the maximum, but POD activity in Si(-) rice plants was lower. These results suggested that silicon could enhance the harmony of SOD and POD. And silicon had no effect on CAT and PAL activity, but weaken PPO activity (Fig.3). After being inoculated with R. solani, the Si(+) rice plants had significantly lower disease index with relative control effect of 1/4 compared to the Si(-) rice plants (Table 2).

Immunity, Innate↗
PubMed2006

[En block frontal-temple silicone for humping the forehead and temple].

OBJECTIVE: To explore the reliability of humping the forehead and temple by en block frontal temporal silicone . METHODS: Make wax mold by piling up wax slices layer by layer according to the rang of depressing of the forehead and temple, the section being humped and the hight need to be projected. Order the silicone block according to the dimension of the wax mold. Make the implant from the silicon block. Under local anaesthesia dissection under the superficial temporal fascia and galea through forehead and two temporal incisions. Implant the silicon through the middle incision. RESULTS: Total 18 cases in this group were followed up for 3-12 months. Wound healed primarily without infection. I case with early blood effusion cured after aspiration. l case with later clear effusion cured after aspiration ad injection of prednisone in to the capsular. The frontal temporal contours were satisfactory . No outline of the implant was seen. CONCLUSION: It is safety and satisfied to hump the forehead and temple by en block frontal temporal silicone.

Adult↗
PubMed1991

[Immunohistochemical findings of epiretinal membranes after silicone oil injection].

During vitreoretinal surgery, 23 epiretinal membranes from eyes treated with silicone oil were removed. They were examined by immunohistochemical methods and compared with 15 membranes from eyes affected by proliferative vitreoretinopathy (PVR) and not treated with silicone oil and with 4 membranes from eyes with intermediate uveitis. PVR membranes from eyes treated with silicone oil showed a high level of macrophages and a strong expression of HLA-DR. Additionally, lymphocytes were found in PVR membranes, a finding that has not been described before. Similar changes were seen in proliferations removed from eyes affected by uveitis, but these membranes were found to have smaller amounts of extracellular substance. In contrast to this, most cells in the PVR membranes from eyes not treated with silicone oil react with vimentin, GFAP and cytokeratin. In none of these membranes were we able to find T-lymphocytes. It is not possible to say whether or not the different findings are attributable ot the silicone oil.

Extracellular Matrix↗
PubMed1991

Temporary closure of the abdominal wall by use of silicone rubber sheets after operative repair of ruptured abdominal aortic aneurysms.

Management of patients after operative repair of abdominal aortic aneurysms can be further complicated if primary closure of the abdominal wall cannot be technically accomplished or is associated with profound increases in intraabdominal and peak inspiratory pressures. We recently treated five patients with ruptured abdominal aortic aneurysms and one patient with a ruptured thoracoabdominal aneurysm whose abdominal incisions had to be closed with a Dacron reinforced, silicone sheet. All patients were hemodynamically unstable either at admission to the hospital or became so during operation. Four patients required the insertion of a silicone rubber sheet at the primary operation because of massive retroperitoneal hematoma or edema of the bowel wall or both. Incisions in two patients were closed primarily, but the patients required reexploration and secondary closure with silicone rubber sheets because of the development of marked increases in peak inspiratory pressures, intraabdominal pressures, and decreased urinary output. Four of the six patients subsequently underwent successful removal of the silicone rubber sheets with delayed primary closure of the abdominal wall, and two others died before removal. The patient with the ruptured thoracoabdominal aneurysm died on postoperative day 20 because of pulmonary sepsis but had a healed abdominal incision. The three surviving patients have been discharged. A silicone rubber sheet may be necessary for closure of the abdominal wall after repair of ruptured abdominal aortic aneurysm in patients where primary abdominal wall closure is impossible or where it results in compromise in respiratory or renal function.

Abdomen↗
PubMed1990

Inhibition of superoxide dismutase activity by silicon.

Elevated silicon levels have been found in the serum of uremic patients, in the brain of patients with senile dementia and in neuroglial tangles of Alzheimer patients. The effect of silicon on superoxide dismutase was studied in vitro, since excessive superoxide production occurs in renal failure, in inflammatory conditions and in the aging process. Silicon in concentrations similar to those found in serum of uremic patients inhibits superoxide dismutase activity. The degree of inhibition is directly proportional to silicon levels. Depression of superoxide dismutase by Si is likely to result in a decrease in oxygen free radical destruction and thus an increase in excessive local availability of oxygen free radicals. The increased silicon levels in brain, kidney, lung and RBC which are especially sensitive to oxygenation damage may contribute to a variety of important clinical complications, by means of excess oxygen free radicals.

Animals↗
PubMed1990

Deposits of crystalline material containing silicon in surgically excised human valves.

Ninety-seven surgically excised natural cardiac valves were examined by scanning electron microscopy and x-ray energy spectroscopy to assess the occurrence of crystalline deposits that contain the element silicon. Valves examined included 33 mitral valves, 63 aortic valves, and 1 tricuspid valve. To reduce the possibility of surface contamination, the deep layers of some valves were examined after exposure by fracture of the valve. Crystalline material containing silicon was observed in the deep tissue. Such crystalline material was sometimes entwined within subendothelial fibers. Crystalline deposits that contained silicon were associated with 34 of 97 of these valves (35%). Among the 34 valves that showed silicon, 24 (71%) also showed microdeposits of calcific material. In view of evidence that silicon may participate in the calcification of bone, and is found in the intima of arteries, a role for this element in ectopic calcification of valves may exist.

Adult↗
PubMedDate not supplied

Lymphadenopathy secondary to silicone hand joint prostheses.

The occurrence of lymphadenopathies was investigated in 23 patients with diverse rheumatic conditions who had silastic prosthesis in joints of the hands, to determine whether these adenopathies were due to the presence of silicone particles. Five cases had clinically detectable lymph node enlargement and tissue samples were studied by light and scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA). In 3 out of the 5 cases foreign body granulomas were observed by light microscopy, SEM showing a highly irregular distribution of foreign body material with a peak for silicone by EDXA. Foreign body particle distribution closely correlated with silicone concentration. No granulomas were found in the two remaining patients with adenopathies who presented a non-specific reactive lymphadenitis. Our findings show that silicone lymphadenopathy is a more frequent complication (13%) of silastic arthroplasty than is usually recognized and therefore should be considered in the differential diagnosis of patients with lymph node enlargement who have previously received a silicone arthroplasty.

Adult↗
PubMed1990

[Loss of corneal endothelial cells following pars plana vitrectomy and silicone oil implantation].

Endothelial cell loss contributes to severe corneal decompensation following pars plana vitrectomy and silicone oil injection into the vitreous cavity. The corneal endothelium of 35 eyes (35 patients) was evaluated prospectively before and after pars plana vitrectomy in a clinical study by means of wide field specular microscopy (Roberts and Koester). Special attention was paid to differences between patients with and without silicone oil in the anterior chamber with respect to postoperative complications and endothelial cell loss. In 12 of the 35 eyes silicone oil was present in the anterior chamber. After a 6-month follow-up we found in all 35 eyes an average decrease in endothelial cell density of 22.9% +/- 13.3% compared to the preoperative values. A correlation between pre- and postoperative cell density (r = 0.827) after six months could be demonstrated. Logistic regression was used to estimate the statistical significance of various factors influencing endothelial cell loss such as inflammatory anterior chamber reaction, elevated intraocular pressure and silicone oil in the anterior chamber. Silicone oil in the anterior chamber was proved to be the main factor causing endothelial cell loss (p less than 0.025). Age group and number of previous intraocular surgical procedures showed no significant influence on endothelial cell loss.

Adult↗
PubMed1990

[The evaluation of intracordal silicone injection in patients with postoperative recurrent nerve paralysis].

This study aimed to evaluate the usefulness and efficacy of intracordal silicone injection in the treatment of cordal paralysis after thoracic surgery or due to tumor invasion of the recurrent nerve. A total of twenty two patients with cordal paralysis was treated with this procedure. The cause of the cordal paralysis was injury to the recurrent nerve incurred during operation for oesophageal or lung cancer in nineteen patients, and direct invasion of malignant neoplasm to the recurrent nerve in the other three patients. Among the nineteen postoperative patients, fifteen underwent silicone injection 15 to 75 days after thoracic operations during hospitalization. The other four patients were treated after discharge from the hospital. The complaints of the fifteen patients who were treated during hospitalization were dysphonia, aspiration and inability to remove sputum. After treatment, dysphonia had improved in all of these fifteen patients, and aspiration had disappeared in thirteen patients. In four patients who were treated with this procedure 7 months following thoracic operation and three who had cordal paralysis due to invasion of malignant tumors, in all of whom aspiration had not been noted, dysphonia disappeared completely after the silicone injection. To evaluate the effect of silicone injection on the patients' cough force, the intratracheal pressure during cough was measured in patients before and immediately after the treatment. The maximum intrathecal pressure was 25 (+/- 16.57) mmHg before silicone injection. After the procedure, the maximum pressure rose to 95 (+/- 18.13) mmHg. Following the procedure, the patients who had suffered severe debilitating aspiration could remove sputum easily.

Adult↗
PubMed1989

[Evaluation of accuracy and the time-dependent dimensional stability of silicone based impression materials].

In the recent years, silicone elastomeric impression materials are widely used in prosthetic dentistry. The accuracy and dimensional stability of these silicone elastomeric impression materials affect the success in their clinical usage. In this study, accuracy and the time-dependent dimensional stability of silicone based impression materials were evaluated. The effect of time is important when using silicone elastomeric impression materials. The result of this study clearly indicated that the silicone impression should be poured as soon as possible.

Dental Impression Materials↗
PubMed1989

[Setting expansion of dental stone in hydrophilic addition type silicone impression].

The setting expansion of a dental stone poured in addition silicone impression materials was evaluated. Impressions were made of two different addition silicones (hydrophilic and hydrophobic) that had three different consistencies (injection, regular and putty). A dental stone which did not contain any additives was poured in the impressions and the setting expansion of the stone was automatically measured using an electric micrometer and a computer. The setting expansion of the stone that was poured in the impression did not significantly vary with the consistency of the silicones. On the other hand, the setting expansion of the stone in the hydrophilic silicone was significantly larger than that in hydrophobic silicone.

Calcium Sulfate↗