The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Ruth E. Cameron - One of the best experts on this subject based on the ideXlab platform.
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Effect of processing route and acetone pre-treatment on the biostability of Pellethane materials used in medical device applications.
Biomaterials, 2005Co-Authors: Jennifer Taylor, Peter R. Laity, Sharlene Freeburn, S. S. Wong, Keith Norris, Peck Khunkamchoo, Martin Cable, Geoffrey Thomas Andrews, A. F. Johnson, Ruth E. CameronAbstract:Thermoplastic polyurethanes, such as Pellethane 2363 80A (Pel80A) and Pellethane 2363 55D (Pel55D) are widely used in the medical device industry because of their biological and mechanical properties. However, premature failure in such devices has been observed and attributed to environmental stress cracking (ESC). The current work investigates the possibility of reducing ESC via bulk morphology manipulation. This can be achieved through various processing routes such as solvent-casting (SC) and hot-press quenching (HPQ). The effect of stress on the bulk morphology of Pel55D and Pel80A was evaluated using small-angle X-ray scattering (SAXS) in conjunction with tensile testing. SC samples exhibited greater phase separation compared with HPQ samples. Alignment of hard segment domains became apparent around the point of yield. Onset of ESC with respect to SC and HPQ routines was determined using the Zhao-Stokes glass-wool test with optical (OM) and environment scanning electron microscopy (ESEM). Improvement in biostability of Pel80A was found in HPQ samples compared to those that were SC. A secondary objective of this work was to investigate the effect of acetone pre-treatment on surface morphology. High resolution imaging of acetone treated and untreated SC Pel80A showed significant differences in surface morphology.
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analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model part ii in vivo investigation
Biomaterials, 2005Co-Authors: Imran Khan, Nigel J Smith, Eric Jones, Dudley Finch, Ruth E. CameronAbstract:Abstract The polyurethane (PU) elastomer Corethane 80A (Corvita) is being considered as the acetabular bearing material in a novel total replacement hip joint. Its biostability was investigated in vitro (Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part I: material selection and evaluation, Biomaterials, in press) together with three other commercially available biomedical PUs: Pellethane 2363-80A (DOW Chemical), a polyhexamethylene oxide based PU, PHMO-PU (CSIRO, not supplied as a commercial product) and ChronoFlex AL-80A (CardioTech). From the in vitro studies, Corethane 80A displayed the best overall resistance to hydrolysis, ESC, MIO and calcification, followed by ChronoFlex 80A and PHMO-PU, with Pellethane 80A being the least stable. Building on the in vitro investigation, the follow-up in vivo study (reported here) assessed Corethane 80A as the bearing layer in a prototype compliant layer acetabular cup, in a fully functioning ovine total hip arthoplasty (THA) model. PU degradation in the retrieved cups was analysed using a range of analytical and physical-testing methods including mechanical testing, differential scanning calorimetry, Fourier transform infrared spectroscopy and environmental scanning electron microscopy. The Corethane 80A functioned well in the THA model, with the bearing surfaces of the retrieved hip cups showing no significant evidence of biodegradation or wear damage after 3 years in vivo. The findings in this study provide compelling evidence for the biostability and effectiveness of acetabular cups incorporating a Corethane 80A compliant bearing layer.
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Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part II: in vivo investigation.
Biomaterials, 2005Co-Authors: Imran Khan, Nigel J Smith, Eric Jones, Dudley Finch, Ruth E. CameronAbstract:The polyurethane (PU) elastomer Corethane 80A (Corvita) is being considered as the acetabular bearing material in a novel total replacement hip joint. Its biostability was investigated in vitro (Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part I: material selection and evaluation, Biomaterials, in press) together with three other commercially available biomedical PUs: Pellethane 2363-80A (DOW Chemical), a polyhexamethylene oxide based PU, PHMO-PU (CSIRO, not supplied as a commercial product) and ChronoFlex AL-80A (CardioTech). From the in vitro studies, Corethane 80A displayed the best overall resistance to hydrolysis, ESC, MIO and calcification, followed by ChronoFlex 80A and PHMO-PU, with Pellethane 80A being the least stable. Building on the in vitro investigation, the follow-up in vivo study (reported here) assessed Corethane 80A as the bearing layer in a prototype compliant layer acetabular cup, in a fully functioning ovine total hip arthoplasty (THA) model. PU degradation in the retrieved cups was analysed using a range of analytical and physical-testing methods including mechanical testing, differential scanning calorimetry, Fourier transform infrared spectroscopy and environmental scanning electron microscopy. The Corethane 80A functioned well in the THA model, with the bearing surfaces of the retrieved hip cups showing no significant evidence of biodegradation or wear damage after 3 years in vivo. The findings in this study provide compelling evidence for the biostability and effectiveness of acetabular cups incorporating a Corethane 80A compliant bearing layer.
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analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model part i materials selection and evaluation
Biomaterials, 2005Co-Authors: Imran Khan, Nigel J Smith, Eric Jones, Dudley Finch, Ruth E. CameronAbstract:The polyurethane elastomer (PU) Corethane 80A (Corvita) is being considered as the acetabular bearing material in a novel total replacement hip joint. The biostability of Corethane 80A was investigated in vitro (this work) and in vivo (reported separately) in a fully functioning ovine total hip arthroplasty (THA) model, with the PU as the bearing layer in a prototype compliant layer acetabular cup. The in vitro studies assessed the resistance of Corethane 80A to the main degradation mechanisms observed in PUs: hydrolysis, environmental stress cracking (ESC), metal ion oxidation (MIO) and calcification. The performance of the polycarbonate PU Corethane 80A was assessed alongside three other commercially available biomedical PUs: polyether PUs Pellethane 2363-80A (DOW Chemical) and PHMO-PU (CSIRO, not supplied as a commercial material) as well as polycarbonate PU ChronoFlex AL-80A (CardioTech). Chemical and structural variables that affect the properties of the materials were analysed with particular attention to the nature of the material's hard and soft segments. PU degradation was probed using a range of analytical tools and physical-testing methods, including mechanical testing, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and environmental scanning microscopy (ESEM). Corethane 80A displayed the best overall resistance to hydrolysis, ESC, MIO and calcification, followed by ChronoFlex 80A and PHMO-PU. Pellethane 80A was the least stable. This study provides compelling evidence for the biostability and effectiveness of Corethane 80A and points to its suitability for use as a compliant bearing layer in hip arthroplasty, and possibly also other joints.
S. L. Cooper - One of the best experts on this subject based on the ideXlab platform.
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Improved materials for blood-contacting applications: blends of sulphonated and non-sulphonated polyurethanes
Journal of Materials Science: Materials in Medicine, 1992Co-Authors: R. W. Hergenrother, S. L. CooperAbstract:Propyl sulphonate groups were grafted on to the urethane nitrogens of Pellethane 2363-80A at three levels: 1.2, 14, and 50%. Blends with an effective level of 1.2 and 14% were made by blending the 14 and 50% sulphonated polyurethanes with the unsubstituted material. Tensile testing was performed on the materials in both their dry and hydrated state. The blend materials exhibited a small improvement in tensile strength over their bulk analogues. Dynamic contact angle and X-ray photoelectron spectroscopy (XPS) showed an enrichment of sulphonate groups at the surface of the blend materials compared to bulk samples of the same overall composition. Canine ex vivo shunt experiments revealed fewer platelets adherent and less platelet spreading on the blend materials than on the bulk materials with the same level of sulphonation. This suggests that sulphonated polyurethanes can be developed that have improved blood compatibility while maintaining good physical properties in an aqueous environment.
Jeff Mahon - One of the best experts on this subject based on the ideXlab platform.
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Novel Water Loving Coatings (WLC) Lubricious and Durable Guidewires
2017 Design of Medical Devices Conference, 2017Co-Authors: Peter A. Edwards, Nick Nimchuk, Michael Price, Jeff MahonAbstract:Hydrophilic coatings applied to guidewires or catheters, lower friction of the device thus improves handling and reduces damage to the vessel walls during access, delivery and retrieval. Peripheral guidewires typically consist of a polymer jacket, basecoat and topcoat. The polymer jacket is highly radiopaque for fluoroscopy visualization. Basecoat adheres to the polymer jacket and hydrophilic topcoat. Basecoat and topcoat play important roles towards coating device durability and lubricity. Water Loving Coatings (WLC) are the first developed 510(k) clearance guidewires utilizing epoxy polyurethane technology. Coatings are non-hemolytic and non-cytotoxic. WLC are advances toward glycidyl carbamate (GC) resins. Linear Glycidyl Carbamates have shown excellent flexibility based off structure property relationships [1]. Water dispersible GC (WD-GC) oligomers have been prepared by additions of poly(ethylene glycol) methyl ether (m-peg) to isocyanurate and biuret, then end capped with glycidol [2]. WLC technologies are lubricious and durable water dispersible polyurethane or polyurea glycidyl carbamates [3]. Modified Hyaluronate with WD-GC oligomers have shown increases in lubricity of Guidewires when used with a catheter [4]. WLC coatings have been applied to a micro-wire to reduce endothelial mechanical lining damage [5]. Common thermoplastic urethanes (TPU), similar to WLC morphology, used in the medical industry, are: Biomer and Lubrizol’s Pellethane®, Tecoflex™ and Estane™. Biomer consists of 4,4′-Methylenebis(phenyl isocyanate) (MDI), Ethylenediamine (EDA), and Polytetramethylene diol (Poly THF). Pellethane consists of MDI, 1,4-Butanediol (BDO) and Poly THF. Tecoflex consists of 4-4′-methylenebis (cyclohexyl isocyanate) (H12MDI), BDO and Poly THF. Medical grade Estane is an ester of adipic acid with BDO for soft segments and MDI and BDO for hard segments. TPU structure and morphology dictates polymeric properties.
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Novel Water Loving Coatings (WLC) Lubricious and Durable Guidewires
2017 Design of Medical Devices Conference, 2017Co-Authors: Peter A. Edwards, Nick Nimchuk, Michael Price, Jeff MahonAbstract:Hydrophilic coatings applied to guidewires or catheters, lower friction of the device thus improves handling and reduces damage to the vessel walls during access, delivery and retrieval. Peripheral guidewires typically consist of a polymer jacket, basecoat and topcoat. The polymer jacket is highly radiopaque for fluoroscopy visualization. Basecoat adheres to the polymer jacket and hydrophilic topcoat. Basecoat and topcoat play important roles towards coating device durability and lubricity. Water Loving Coatings (WLC) are the first developed 510(k) clearance guidewires utilizing epoxy polyurethane technology. Coatings are non-hemolytic and non-cytotoxic. WLC are advances toward glycidyl carbamate (GC) resins. Linear Glycidyl Carbamates have shown excellent flexibility based off structure property relationships [1]. Water dispersible GC (WD-GC) oligomers have been prepared by additions of poly(ethylene glycol) methyl ether (m-peg) to isocyanurate and biuret, then end capped with glycidol [2]. WLC technologies are lubricious and durable water dispersible polyurethane or polyurea glycidyl carbamates [3]. Modified Hyaluronate with WD-GC oligomers have shown increases in lubricity of Guidewires when used with a catheter [4]. WLC coatings have been applied to a micro-wire to reduce endothelial mechanical lining damage [5]. Common thermoplastic urethanes (TPU), similar to WLC morphology, used in the medical industry, are: Biomer and Lubrizol’s Pellethane®, Tecoflex™ and Estane™. Biomer consists of 4,4′-Methylenebis(phenyl isocyanate) (MDI), Ethylenediamine (EDA), and Polytetramethylene diol (Poly THF). Pellethane consists of MDI, 1,4-Butanediol (BDO) and Poly THF. Tecoflex consists of 4-4′-methylenebis (cyclohexyl isocyanate) (H12MDI), BDO and Poly THF. Medical grade Estane is an ester of adipic acid with BDO for soft segments and MDI and BDO for hard segments. TPU structure and morphology dictates polymeric properties.
Thomas Chassé - One of the best experts on this subject based on the ideXlab platform.
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oxygen plasma surface treatment of polymer films Pellethane 55de and epr g vtms
Applied Surface Science, 2021Co-Authors: Ivana Mrsic, Tim Bäuerle, Steffen Ulitzsch, Günter Lorenz, Karsten Rebner, Andreas Kandelbauer, Thomas ChasséAbstract:Abstract A systematic study using a central composite design of experiments (DoE) was performed on the oxygen plasma surface modifications of two different polymers—Pellethane 2363-55DE, which is a polyurethane, and vinyltrimethoxysilane-grafted ethylene-propylene (EPR-g-VTMS), a cross-linked ethylene-propylene rubber. The impacts of four parameters—gas pressure, generator power, treatment duration, and process temperature—were assessed, with static contact angles and calculated surface free energies (SFEs) as the main responses in the DoE. The plasma effects on the surface roughness and chemistry were determined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Through the sufficiently accurate DoE model evaluation, oxygen gas pressure was established as the most impactful factor, with the surface energy and polarity rising with falling oxygen pressure. Both polymers, though different in composition, exhibited similar modification trends in surface energy rise in the studied system. The SEM images showed a rougher surface topography after low pressure plasma treatments. XPS and subsequent multivariate data analysis of the spectra established that higher oxidized species were formed with plasma treatments at low oxygen pressures of 0.2 mbar.
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Oxygen plasma surface treatment of polymer films—Pellethane 55DE and EPR-g-VTMS
Applied Surface Science, 2020Co-Authors: Ivana Mrsic, Tim Bäuerle, Steffen Ulitzsch, Günter Lorenz, Karsten Rebner, Andreas Kandelbauer, Thomas ChasséAbstract:Abstract A systematic study using a central composite design of experiments(DoE) was performed on the oxygen plasma surface modifications of two different polymers—Pellethane 2363-55DE, which is a polyurethane, and vinyltrimethoxysilane-grafted ethylene-propylene (EPR-g-VTMS), a cross-linked ethylene-propylene rubber. The impacts of four parameters—gas pressure, generator power, treatment duration, and process temperature—were assessed, with static contact angles and calculated surface free energies (SFEs) as the main responses in the DoE. The plasma effects on the surface roughness and chemistry were determined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Through the sufficiently accurate DoE model evaluation, oxygen gas pressure was established as the most impactful factor, with the surface energy and polarity rising with falling oxygen pressure. Both polymers, though different in composition, exhibited similar modification trends in surface energy rise in the studied system. The SEM images showed a rougher surface topography after low pressure plasma treatments. XPS and subsequent multivariate data analysis of the spectra established that higher oxidized species were formed with plasma treatments at low oxygen pressures of 0.2 mbar.
James M. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Adhesion and cytokine production by monocytes on poly(2- methacryloyloxyethyl phosphorylcholine-co-alkyl methacrylate)-coated polymers
Journal of Biomedical Materials Research, 1995Co-Authors: Kristin M. Defife, J. K. Yun, A. Azeez, S. Stack, Kazuhiko Ishihara, Nobuo Nakabayashi, Erica Colton, James M. AndersonAbstract:Human monocytes isolated from peripheral venous blood were assayed for their ability to adhere to various polymers. The culture supernatants were also assayed for the cytokines, interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). The polymers evaluated for adherence and cytokine production included Pellethane®, polyethylene and poly[n-butyl methacrylate (BMA)] coated with poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-alkyl methacrylate] copolymers. In some experiments the test polymers were adsorbed with fibrinogen or IgG prior to the addition of monocytes. MPC copolymer-coated materials inhibited monocyte and macrophage adhesion after 1 and 8 days of culture relative to corresponding uncoated polymers and tissue culture polystyrene (TCPS). The degree of inhibition by coated Pellethane compared to uncoated Pellethane was the greatest, while inhibition of adhesion by coated poly(BMA) was the least compared to uncoated poly(BMA). However, adhesion was significantly decreased on both coated and uncoated poly(BMA) by day 8. While IL-1β, IL-6, and TNF-α release was variably influenced by polymer coating, release was consitently inhibited relative to TCPS on day 1. However, cytokine production was not inhibited compared to corresponding uncoated polymers on day 1. With or without protein preadsorption, IL-1β release was not detectable in the supernatants of any polymer on day 8, IL-6 production was diminished on day 8, and TNF-α production was sustained on day 8. Overall, MPC copolymercoated and uncoated poly(BMA) were the least stimulating, while TCPS was the most stimulating. These studies suggest that MPC copolymers may improve the cell adhesion-resistant properties of a biomaterial while variably influencing the activation of cells which may contact the coated surface. © 1995 John Wiley & Sons, Inc.
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Oxidative biodegradation mechanisms of biaxially strained poly(etherurethane urea) elastomers.
Journal of Biomedical Materials Research, 1995Co-Authors: Mark A. Schubert, Anne Hiltner, Michael J. Wiggins, Michael P. Schaefer, James M. AndersonAbstract:As part of ongoing studies in polyurethane biostability and biodegradation, we have investigated an in vitro system to test strained poly(etherurethane urea) (PEUU). Recently, we utilized this system to reproduce in vivo stress cracking in strained Pellethane. In this study, strained PEUU was tested to determine whether it degrades through a common mechanism with Pellethane and to further examine the steps involved in this degradation. Biaxially strained PEUU elastomers were treated with an alpha 2-macroglobulin (alpha 2-Mac) protein solution followed by an oxidative H2O2/CoCl2 treatment. Characterization of the strained PEUU specimens was performed with attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), electron spectroscopy for chemical analysis, and contact angle analysis. The results from these characterization techniques provide conclusive evidence that biodegradation of PEUU and Pellethane occurs through a common mechanism. Chemical changes to the PEUU include cleavage of the polyether soft segments and urethane linkages, leaving the hard segment domains unaffected. SEM analysis shows that this chain cleavage leads to the development of severe pitting and cracking of the PEUU surface. In addition, the in vitro degradation accurately reproduces the in vivo degradation chemically and physically. This result verifies that the primary species responsible for biodegradation of PEUUs, in vivo, are hydroxyl and/or hydroperoxide radicals. alpha 2-Mac pretreatment increases the rate of degradation compared to direct treatment in H2O2/CoCl2. As the PEUU soft segment chains are cleaved, the degradation products are extracted into the treatment solution or environment. Finally, a new biodegradation mechanism of PEUUs is presented that involves crosslinking of the polyether soft segments.
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Human plasma α2-macroglobulin promotes in vitro oxidative stress cracking of Pellethane 2363-80A : in vivo and in vitro correlations
Journal of Biomedical Materials Research, 1993Co-Authors: Q. Zhao, James M. Anderson, Amy K. Mcnally, K. R. Rubin, M. Renier, V. Rose-caprara, A. Hiltner, Peter Urbanski, Kenneth B. StokesAbstract:It is hypothesized in this study that the phenomenon of environmental stress cracking (ESC) in polyetheruethane is caused by a synergistic action of biological components in the body fluids, oxidative agents, and stress. An in vitro system is designed to mimic the in vivo system; human plasma contains certain biological components that can act as a stress cracking promoter, while H2O2 (Co) solution provides an oxidative reaction comparable to that observed in the respiratory burst of adherent macrophages and foreign-body giant cells. It is demonstrated that the phenomenon of in vivo stress cracking in Pellethane 2363-80A is duplicated by an in vitro system that involves a pretreatment of prestressed specimens with human plasma at 37°C for 7 days followed by oxidation in 10% hydrogen peroxide with 0.10M cobalt chloride at 50°C for 10 days. The pretreatment with plasma has a synergistic effect with the oxidation by H2O2 (Co) treatment to produce ESC. A plasma component responsible for promoting stress cracking in Pellethane polyurethane is identified to be α2-macroglobulin (α2M). © 1993 John Wiley & Sons, Inc.
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In vivo leucocyte interactions on Pellethane® surfaces
Biomaterials, 1990Co-Authors: Michael R. Brunstedt, James M. Anderson, Karen L. Spilizewski, Roger E. Marchant, Anne HiltnerAbstract:Abstract In vivo leucocyte interactions of three Pellethane® materials of varying hardness were qualitatively and quantitatively characterized using a cage implant system over a 21 d implantation period. Scanning electron microscopy (SEM) and cytochemical staining were utilized to observe the cellular events occurring at the leucocyte-biomaterial interface. Many of the quantitative assays performed, the intracellular alkaline phosphatase activity of exudate leucocytes, the intracellular acid phosphatase activity of adherent leucocytes, the density of adherent leucocytes and the foreign body giant cell network formation tendencies of adherent leucocytes, suggest increased cellular activation with increased Pellethane® hardness. Qualitative SEM evaluation of Pellethane® surfaces revealed a variety of cellular activities. These included macrophage adherence, cytoplasmic spreading and macrophage-macrophage membrane fusions to form foreign body giant cells. The foreign body giant cells exhibited nuclear reorganization and, when compared with adherent macrophages, they displayed an enhanced ability to fuse to neighbouring leucocytes, increased spreading of membrane processes over the polymer surface, the presence of large cytoplasmic vacuoles, and a lengthened duration of enzymatic activity. Contact angle analysis showed the Pellethane® surfaces to be hydrophobic and of low hysteresis. The critical surface tension and the dispersive component of the total surface tension were found to increase with Pellethane® hardness.
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Cellular interactions with biomaterials: in vivo cracking of pre-stressed Pellethane 2363-80A.
Journal of Biomedical Materials Research, 1990Co-Authors: Q. Zhao, James M. Anderson, A. Hiltner, Kenneth B. Stokes, M. P. Agger, M. Fitzpatrick, Peter UrbanskiAbstract:The phenomenon of stress cracking of Pellethane 2363-80A (PEU) was investigated using the cage implant system. A cytotoxic polyvinylchloride (PVC) and a silicone rubber containing an anti-inflammatory steroid were used to create inflammatory environments in which the biostability of the pre-stressed PEU was tested. These coimplants provided alternative in vivo environments to study in vivo polymer interactions. The inflammatory responses to the implanted cages were monitored by analyzing the exudates aspirated from the cages at different implantation times over 21 days. The pre-stressed PEU specimens were retrieved after 5, 10, and 15 weeks postimplantation and examined by optical microscopy (OM) and scanning electron microscopy (SEM). The results support the conclusion that in vivo cracking of stressed (strained) Pellethane 80A is related to cell-polymer interactions. Severe cracking or rupture of the implanted PEU specimens was observed as early as 5 weeks postimplantation. Molecular chain degradation of the implanted specimens was evident from molecular weight measurements. Neither surface cracking nor degradation of macromolecules was found on the pre-stressed PEU specimens with the added cytotoxic PVC implanted over 15 weeks. No cracking was observed on the pre-stressed specimens in the presence of steroid silicone rubber, even after 10 weeks implantation.