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At least 19 recordsLinked to original sources
PubMed1977

Development of blood-compatible elastomers. V. Surface structure and blood compatibility of avcothane elastomers.

The Avcothane 51 elastomer, a member of a series of proprietary materials best characterized as polyurethane/poly(dialkylsiloxane) block copolymers, displays considerable hemocompatibility without any incorporated anticoagulants. In the form of intra-aortic balloons, the elastomer was implanted in several thousands of cardiac patients without intolerable hematologic effects. Hemocompatibility has been assumed to result from a predominantly dispersion-type surface force field whose intensity fluctuates within small domains, maintaning adsorbed blood proteins in an unstable state. The relative hemocompatibility of films, which were obtained from a prepolymer solution cast on substrates impenetrable to the solvent, is a function of the effective surface molecular structure. This can vary as a function of preparative conditions (temperature and rate of evaporation), and has been correlated with an anisotropic distribution of the silicone component in cured films. The concentration of this component in surface layers was quantified independently by IRATR spectroscopy and electron-microprobe analysis, giving consistent results. An IRATR index, which is computed from the ratio of absorptivities measured at 13.00 and 12.62 mu and is inversely proportional to the relative silicone content of surface layers, was found to correlate with the apparent hemocompatibility determined by different in vitro methods. Optimized reproducible hemocompatibility is attained by strict process controls.

Assisted Circulation↗
PubMed1993

Permeability of latex and thermoplastic elastomer gloves to the bacteriophage phi X174.

BACKGROUND: Most studies challenging the integrity of the glove barrier have compared the permeability of vinyl and latex gloves. However, no studies of a new nonlatex, nonvinyl thermoplastic elastomer have been reported. This pilot study therefore compared the protective barriers provided by latex and thermoplastic elastomer surgical gloves against penetration of the bacteriophage phi X174. METHODS: Twenty thermoplastic elastomer gloves and 25 commercially available latex gloves (20 brand 1, 5 brand 2) were filled with a sterile serum surrogate and exposed to the phi X174 virus in a flask, with shaking for 180 minutes at 37 degrees C. Aliquots of 5 ml were withdrawn at baseline, 30, 60, 120, and 180 minutes and assayed by a standard plaque assay. The remaining contents of the gloves were then tested by an extremely sensitive qualitative assay (plaque assay without dilution of the sample). RESULTS: With the standard plaque assay, virus was detected in 30% of the brand 1 latex gloves, in 80% of the brand 2 latex gloves, but in none of the thermoplastic elastomer gloves. The qualitative assay, which can detect even a single virus in the entire glove contents, had positive results for 30% of the thermoplastic elastomer gloves, 70% of the brand 1 gloves, and 100% of the brand 2 gloves. CONCLUSIONS: Despite the small sample, the results of this stringent assay suggest that the mechanical barrier offered by thermoplastic elastomer gloves is equal to or better than that provided by the latex gloves tested. Clinical studies are needed to evaluate thermoplastic elastomer gloves, which may withstand mechanical stress better than latex or vinyl. Thermoplastic elastomer gloves may therefore be a desirable alternative for health care workers in high-risk settings or for individuals with latex allergies.

Bacteriophages↗
PubMed1991

In vivo study of an elastomer end-coated polytetrafluoroethylene vascular prosthesis.

Polyurethane end-coated polytetrafluoroethylene (PTFE) grafts (elastomer PTFE grafts) were implanted in 12 female adult mongrel dogs to assess patency, intimalization, tissue incorporation, and technical suitability of the material as a vascular graft. Each dog had bilateral aortoiliac grafts placed, one a standard PTFE and the other an elastomer PTFE graft. The length of the grafts was 7-8 cm and the diameter was 6 mm. The grafts were harvested at intervals to 120 days postoperatively. The elastomer PTFE grafts showed superior longitudinal elasticity, retention of shape, and no graft tearing with suture tension; however, no significant difference in bleeding was noted at the anastomoses between the standard and elastomer PTFE grafts. Satisfactory patency was obtained with both standard (8/10) and elastomer PTFE grafts (9/10) at 90-120 days. No significant difference in the thickness of intima and the length of pannus ingrowth was noted between the standard and elastomer PTFE grafts. No outer tissue incorporation was seen at the elastomer-treated graft segments as opposed to the well-incorporated untreated segments. In conclusion, elastomer end-coating of a PTFE vascular prosthesis provided excellent handling characteristics without detracting from patency; however, the lack of outer tissue incorporation may be a potential disadvantage in its clinical use.

Anastomosis, Surgical↗
PubMed1995

Clinical effectiveness of fluoride-releasing elastomers. I: Salivary Streptococcus mutans numbers.

The purpose of this study was to examine the effect of fluoride-releasing elastomers on salivary Streptococcus mutans numbers. Twenty-four patients with fixed orthodontic appliances were randomly divided into experimental and control groups consisting of 12 patients each. Conventional elastomers were in place while two baseline whole saliva samples were collected from each subject in both groups at their regular appointments. After the second baseline sample was taken, conventional elastomers were replaced with fluoride-releasing elastomers in the experimental group, whereas conventional elastomers were continued in the control group. Three saliva samples were then collected from all subjects at 1-week intervals. Conventional elastomers were placed in all subjects while two postexperimental saliva samples were collected at regular appointments. Results showed that the control group demonstrated no significant changes (p > 0.05) in the percentage of S. mutans over the 13-week study period. However, after the fluoride-releasing elastomers were placed, the percent of salivary S. mutans decreased significantly (p < 0.01) in the experimental group. There was no significant effect after the fluoride-releasing elastomers were in place for 2 or more weeks.

Adolescent↗
PubMed1999

Color stability and colorant effect on maxillofacial elastomers. Part III: weathering effect on color.

STATEMENT OF PROBLEM: Maxillofacial prostheses are serviceable for approximately 6 months, after which they need to be refabricated because of the deterioration of color and physical properties. PURPOSE: This third article in a 3-part series evaluated the color stability of commonly used colorant-elastomer combinations as a result of exposure to weathering. METHODS AND MATERIAL: Fifteen specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no colorant) for a total of 270 specimens (18 groups of 15 specimens). The 15 specimens of each elastomer-colorant combination were separated into 3 test condition groups (control, time passage, and natural weathering) of 5 specimens per test condition group. Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Color and optical density data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among test conditions (control, time passage, and weathering). When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. RESULTS: Changes in color, as a result of weathering, were noted in many of the colorant-elastomer combinations. Also, color change occurred not only to the colored, but also to uncolored materials over time without exposure to weathering. CONCLUSION: Clinically, the addition of colorants could have a stabilizing effect on the elastomer color when it is exposed to weathering.

Analysis of Variance↗
PubMed2001

Accelerated color change in a maxillofacial elastomer with and without pigmentation.

STATEMENT OF PROBLEM: Maxillofacial prostheses require frequent replacement because the elastomer and its color additives undergo changes. PURPOSE: This study attempted to determine whether predictable color changes occur when 3 pigments are individually incorporated into a specific silicone elastomer. MATERIAL AND METHODS: The materials included an RTV elastomer; 1 natural inorganic pigment, burnt sienna; and 2 synthetic organic pigments, Hansa yellow and alizarin red. Eight test groups of 10 polymerized specimens were established. Groups 1 and 2, acting as the control, involved only the elastomer. Groups 3 and 4 were composed of elastomer and burnt sienna. Groups 5 and 6 consisted of elastomer and Hansa yellow. Groups 7 and 8 comprised elastomer and alizarin red. Odd-numbered groups were assigned to a test site in Miami, Fla., whereas the even numbered groups went to Phoenix, Ariz. Specimens weathered in Miami and Phoenix received sunlight exposures of 1305.7 MJ/m2 and 1310.2 MJ/m2, respectively, over time. Before and after weathering, the L* a* b* color parameter (DeltaE*) of each specimen was determined spectrophotometrically. RESULTS: Mean color changes that occurred in Arizona were larger than those produced in Florida. Specifically, these differences ranged from 0.4 (alizarin red groups) to 2.36 units for the 2 unpigmented control groups. Other differences showed significance for the unpigmented (P=.001), burnt sienna (P=.006), and Hansa yellow groups (P=.001). CONCLUSION: Outdoor weathering tests in which documented ASTM methods were used provided a valid baseline for future research on color changes in maxillofacial prostheses.

Analysis of Variance↗
PubMed1999

Color stability and colorant effect on maxillofacial elastomers. Part II: weathering effect on physical properties.

STATEMENT OF PROBLEM: The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement. PURPOSE: This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure. MATERIAL AND METHODS: Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. RESULTS: Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time. CONCLUSION: The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.

Analysis of Variance↗
PubMed1998

Elastomers for biomedical applications.

Current topics in elastomers for biomedical applications are reviewed. Elastomeric biomaterials, such as silicones, thermoplastic elastomers, polyolefin and polydiene elastomers, poly(vinyl chloride), natural rubber, heparinized polymers, hydrogels, polypeptides elastomers and others are described. In addition biomedical applications, such as cardiovascular devices, prosthetic devices, general medical care products, transdermal therapeutic systems, orthodontics, and ophthalmology are reviewed as well. Elastomers will find increasing use in medical products, offering biocompatibility, durability, design flexibility, and favorable performance/cost ratios. Elastomers will play a key role in medical technology of the future.

Biocompatible Materials↗
PubMed1980

The management of the open perineal wound using a foam elastomer dressing: a prospective clinical trial.

In an attempt to improve the management of the perineal wound after abdominoperineal excision of the rectum we have assessed the value of foam elastomer, a catalysed silicone polymer dressing. The substance has already been used successfully in the treatment of open, granulating wounds at other sites (1). On the fourteenth postoperative day 50 patients with open perineal wounds were randomized to receive either conventional gauze packing or treatment with a foam elastomer dressing. Patients were received weekly until healing occurred. When no cavity remained, a dry dressing alone was used. Initial wound volume was calculated in all patients by forming a foam dressing the volume of which was measured by displacement of water. Healing times were shorter in patients who received foam elastomer, but not significantly so. However, less analgesia (P less than 0.01) and fewer district nurse visits (P less than 0.001) were required by patients in the foam elastomer group. This study suggests that foam elastomer dressing is a more comfortable alternative to a gauze pack in the management of the perineal wound and substantially reduces the amount of nursing supervision which is required. We recommend its routine use in the management of the open perineal wound particularly in the young and cooperative patient.

Adult↗
PubMed1996

The adjuvant effect of silicone gel and silicone elastomer particles in rats.

This study examines the adjuvant properties of silicone oil, silicone gel and silicone elastomer using a foreign antigen, bovine serum albumin (BSA). Seventy male Harlan Sprague-Dawley rats, approximately 250 grams each, were divided into 7 groups: A- incomplete Freund's adjuvant (IFA) with BSA; B- silicone oil with BSA; C- IFA/silicone oil with BSA; D- 50% silicone gel/50% silicone oil with BSA; E- silicone oil/1000 microns elastomer particles with BSA; F- silicone oil/500 microns elastomer particles with BSA; G- saline with BSA. Rats were implanted intramuscularly with mixtures or emulsions of the above described treatment materials. Cardiac punctures were performed on days 0, 14, 28, 42, and 55. Serum IgG antibody response to BSA was determined by enzyme-linked immunosorbent assay (ELISA). Rats were sacrificed on day 55 and sections of the injection sites were collected and stained for histopathologic evaluation. The results demonstrated that silicone gel functions as a potent immunologic adjuvant as measured by a heightened IgG antibody response to BSA. In contrast silicone elastomer particles have no apparent adjuvant effect as determined by the low anti-BSA antibody levels in these treatment groups throughout the course of the study. Histologically, silicone gel and silicone elastomer elicit a moderate to severe "foreign body" granulomatous inflammatory response at the injection site. Silicone oil elicits mild or no local inflammatory response.

Adjuvants, Immunologic↗
PubMed1999

Color stability and colorant effect on maxillofacial elastomers. Part I: colorant effect on physical properties.

STATEMENT OF PROBLEM: The average clinical life span of a maxillofacial prosthesis is approximately 6 months, at which point it needs to be refabricated, mainly because of degradation of the color and physical properties of the prosthesis. PURPOSE: This first part of a 3-part study evaluated the effect of coloring agents on the physical properties of maxillofacial elastomers. METHODS AND MATERIAL: Five dumbbell-shaped and 5 trouser-shaped specimens were fabricated for each of the combinations of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants), for a total of 180 specimens. Evaluations of hardness and tear strength were made with the trouser-shaped specimens. Evaluations of the ultimate tensile strength and the percentage elongation were made with the dumbbell-shaped specimens. A within elastomer analysis compared the 6 colorants using a 1-way analysis of variance for each of the 4 physical properties. When significant differences were observed, the Student-Newman-Keuls multiple range test was used to identify differences between groups at a significance level of.05. RESULTS: Physical properties of maxillofacial elastomers were changed by the incorporation of coloring agents. Dry earth pigments, kaolin, and rayon flocking acted as a solid filler without bonding to the Silicone, and artists' oils and liquid cosmetics acted as a liquid phase without bonding to the silicone matrix. CONCLUSION: No clearly superior colorant-elastomer combination was demonstrated in all the tests in this study.

Analysis of Variance↗
PubMed1998

Silicone elastomer cerebrospinal fluid shunt systems. Council on Scientific Affairs, American Medical Association.

A 1995 resolution of the American Medical Association House of Delegates, introduced by the American Academy of Neurology, the American Association of Neurological Surgeons, and the Congress of Neurological Surgeons, asked the American Medical Association Council on Scientific Affairs to add the use of hardened silicone shunts to its study of the effects of silicone gel used in breast implants. On consideration of the important differences between the two materials, silicone elastomer ("hardened silicone") and silicone gel, the Council on Scientific Affairs elected to address the subject of silicone elastomer shunt systems separately. This report describes the different types of medical-grade silicone used in medical devices, the incidence of hydrocephalus and its causes and treatment, and the use of cerebrospinal fluid shunt systems made of silicone elastomer. Published case reports of possible immunological disease in patients who have had silicone elastomer cerebrospinal fluid shunt systems implanted are reviewed. The Council on Scientific Affairs concluded that the evidence presented does not support the occurrence of immune-mediated systemic reactions to implanted silicone elastomer cerebrospinal fluid shunt systems. The local granulomatous or inflammatory responses observed in some patients with silicone shunt systems have not been shown to be immunologically mediated; similar reactions have been described with other implanted foreign bodies.

Cerebrospinal Fluid Shunts↗
PubMed1995

Color changes in dry-pigmented maxillofacial elastomer resulting from ultraviolet light exposure.

Five dry pigments and one maxillofacial elastomer were evaluated for color changes (delta E) resulting from prolonged exposure to two types of ultraviolet light. The elastomer, pigments, and pigmented elastomers were subjected to each ultraviolet light source for 400, 600, and 1800 hours, and delta E color shifts were determined. The unpigmented elastomer underwent minimally perceptible color change after 600 hours of exposure to both types of ultraviolet light. Two pigments underwent substantial color change after 400 hours, whereas the remaining three pigments remained color stable after 1800 hours. It was concluded that for the materials tested, early color changes in a prosthesis may be the result of degradation of certain ultraviolet light-susceptible pigments, whereas longer term color shifts may be caused by color changes within the elastomer.

Analysis of Variance↗
PubMed1986

Enhanced strength of endothelial attachment on polyester elastomer and polytetrafluoroethylene graft surfaces with fibronectin substrate.

Successful development of a vascular prosthesis lined with endothelium may depend on the ability of the attached cells to resist shear forces after implantation. The purpose of this article is to describe a model for measurement of endothelial detachment caused by shear stress and to identify biomaterials that resist loss of attached cells as a result of shear stress. With human umbilical venous endothelium labeled with indium 111-oxine, cellular attachment to uncoated and fibronectin-coated polyester elastomer and expanded polytetrafluoroethylene (e-PTFE) graft surfaces was quantified after an 18-hour incubation. PTFE grafts prepared by immediate seeding were also studied. The relative strength of endothelial attachment was determined by the percentage of the original inoculum remaining after the seeded graft surfaces were subjected to a physiologic shear stress of 15 dynes/cm2 during in vitro perfusion. In polyester elastomer grafts, fibronectin did not significantly increase initial attachment but did increase the percentage of inoculum remaining after perfusion (92.1% vs. 39.74%, p = 0.001). A similar relationship existed between fibronectin-coated e-PTFE and immediately seeded e-PTFE preparations with 61.6% and 25.8%, respectively, of the inoculum remaining after perfusion (p = 0.001). Furthermore, the percentage of inoculum retained on fibronectin-coated polyester elastomer was significantly greater than on fibronectin-coated e-PTFE (p = 0.001). In comparing uncoated grafts, polyester elastomer had 39.7% of the inoculum retained after perfusion whereas only 1.8% was remaining on the e-PTFE grafts (p = 0.0001). We conclude that polyester elastomer permits better endothelial cell attachment than e-PTFE and that fibronectin coating enhances the strength of attachment to both graft materials.

Biocompatible Materials↗
PubMed1975

Total intravenous nutrition with peripherally inserted silicone elastomer central venous catheters.

Long-term indwelling central venous catheters inserted peripherally for total intravenous nutrition have been complicated by thrombophlebitis in most instances. However, experiences with silicone elastomer catheters used in this manner have not been previously reported. In this investigation a crank introducer unit has been developed that has allowed 61-cm silicone elastomer catheters to be placed in the superior vena cava with insertion in the basillic or cephalic vein. Thirty-five patients (36 catheter placements) received total intravenous nutrition exclusively via these silicone elastomer catheters. The mean time indwelling was 20.4 days (range, four to 56 days). Thirty of the 36 catheters were removed when total intravenous nutrition was discontinued. Only six catheters were removed for nonvenous and venous reactions. These results have shown the safety and efficacy of peripherally inserted silicone elastomer central venous catheters.

Catheterization↗
PubMed1997

Effect of saline exposure on the surface and bulk properties of medical grade silicone elastomers.

Medical-grade silicone elastomers were subjected to accelerated aging in saline to verify the hydrolytic stability of the elastomer. Tensile strength, elongation at break, and the elastomer stress measured at 100% or 200% elongation did not change significantly for peroxide-cured sheeting aged in 37 degrees C or 100 degrees C saline for 45 h. Under similar condition, hydrosilylation cured sheeting behaved similarly; however, increases in stresses measured at 100% and 200% elongation were observed after the first hour of treatment. After the first hour, the physical properties remained relatively constant. On either elastomer, initial liquid drop advancing contact angles for water ranged from 110 degrees to 115 degrees, and in no case was a change of > 6 degrees observed as a result of aging in saline for 45 h at temperatures up to 97 degrees C. The high advancing angles indicated that the surface remained largely hydrophobic. Initial liquid drop receding contact angles ranged from 48 degrees to 64 degrees, with receding contact angles being more sensitive to accelerated aging, in one case decreasing to 14 degrees. Similar decreases in receding contact angle were observed on polyethylene subjected to the same accelerated aging conditions. Decreases in receding contact angle were not considered to be indicative of extensive hydrolysis. The observed contact angle phenomena are consistent with current views of contact angle hysteresis being caused by surface heterogeneity. There was no evidence of significant surface or bulk siloxane hydrolysis under these accelerated aging conditions.

Hydrolysis↗
PubMed2000

Exhaustive soxhlet extraction for the complete removal of residual compounds to provide a nonleaching silicone elastomer.

All commercially available silicone devices contain freely diffusible silicone oils, uncured oligomers, and other impurities (such as catalysts). These residuals have been found in quantities as high as 20% by weight in commercially available silicone medical devices. The fate and effects of these residuals have been the topic of much debate recently. In this study, a method for complete removal of these residual compounds was investigated. The total amount of extractable residuals was determined through exhaustive Soxhlet extraction of 5 silicone elastomers. LIM 6030 had 6.29%, LIM 6070 had 5.74%, Q7-4750 had 3.02%, Q7-4780 had 3.22%, and SE1935 had 0.13% extractables by weight. The amount of silicon containing residuals leaching from both the extracted and nonextracted samples was also evaluated for 3 and 18 days by inductively coiled plasma (ICP) analysis. A significant amount of leachable compounds, reported as microg Si/mg solid sample, was found in all nonextracted elastomers with the exception of SE1935 compared to blanks. The amount of leachable compounds found in the extracted elastomers was not found to be significantly higher than the amount found in the blanks. The residual compounds in silicone elastomers may be completely removed by exhaustive Soxhlet extraction and the resulting polymer does not leach silicon-containing compounds in vitro.

Biocompatible Materials↗