Safety of Silicone Breast Implants (1999) / Chapter Skim
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3 Implant Catalogue
3 Implant Catalogue
Pages 54-79
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From page 54... ...
Consideration should be given to the potential contributions of these influences as well as to the basic influence of silicone ~enericallv or of a specific silicone compound when assessing {A J 1 1 the consequences of breast implantation. Unfortunately, the medical literature describing clinical experience with local and systemic complications of implants has often not specified the make and model of implants or their important characteristics.
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From page 55... ...
Such information would be useful prospectively. The committee concluded that as complete information as possible about the device itself would be helpful to an understanding of the safety of silicone breast implants.
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From page 56... ...
Prevalence of rupture differing by brand of implant has been reported by Feng (IOM Scientific Workshop, 1998) , and Peters and Francel have reported major differences in rupture for silicone gel implants of different vintages, up to 95% at 12 years' implantation with thin shelled, 1972-mid 1980s-implants (France!
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From page 57... ...
There are a number of major construction types of implants. Singlelumen implants have a single silicone elastomer shell traditionally filled with silicone gel.
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From page 58... ...
However, since the 1992 FDA moratorium on gel-filled implants, single-lumen saline implants, that historically comprised 5% of implants (Gabriel et al., 1994; Zones, 1992) , have almost completely replaced gel implants (see Chapter 1~.
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From page 59... ...
Additional data from this group showed silicone gel fluid diffusion from double-lumen implants in greater amounts than from either barriered or unbarriered gel implants (Marrota et al., 1996a)
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From page 60... ...
Shell Polyurethane Coating Texturing was a reaction to the success in reducing capsular contracture of the original 1- or 2-mm-thick poly~ester~urethane foam-textured coating of a regular silicone gel-filled implant (Ashley, 1970, 1972~. The foam was produced from the polymerization of polydiethylene glycol adipate with a 4:1 mixture of 2,4- and 2,6-toluene diisocyanate and was secured by an RTV silicone adhesive primarily to single-lumen gel implants.
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From page 61... ...
was particularly effective in causing an acute and continuing chronic inflammatory response that postponed the mature fibrotic phase and accounted for delayed capsule formation (Brand, 1988; Devor et al., 1993; Sank et al., 1993; Smahel, 1978a; Whalen, 1988) with significantly less contracture than texturing of the silicone shell alone (Handel et al., 1995~.
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From page 62... ...
of women with polyurethane-coated breast implants that were higher than had been considered previously in assessing cancer risks from these implants suggesting that the exposures and risks might be problematic. These risks had been estimated by the FDA at between 5 in 10,000,000 and 111 in 1,000,000 lifetime cancers in women with polyeurethane implants depending on the currently available data or a worst case 100% degradation to 2-4-TDA, respectively.
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From page 63... ...
Implant Shell Texturing The form of texturing of silicone elastomer implant shells varied considerably by manufacturer. For example, Dow Corning Silastic MSI (Micro Structured Implant)
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From page 64... ...
and is indistinguishable from the synovial lining of joints and normal bursae (Copeland et al., 1994; Emery et al., 1994~. Recent analysis proposes that synovium is a transitional phase, inversely related to implant age and unrelated to other factors such as implant surface, placement, and capsule or gel fluid diffusion through the shell (Chase et al., 1996; Ko et al., 1996~.
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From page 65... ...
put silicone gel fluid diffusion at about 300 mg per year, with considerable variation depending on implant age and manufacturer. Figures of 60-100 mg per year for pre-barrier and 5-10 mg per year for barrier implants are quoted frequently in the literature (Independent Advisory Committee on Silicone Gel-Filled Breast Implants, 1992)
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From page 66... ...
Other Characteristics of Implant Shells and Gels Rare shells, like the early polyurethane Ashley implant, had inverted Y-shaped internal dividers, presumably designed to control the shape of the gel and implant, keeping the gel from sagging to the dependent and central part of the implant. This feature was continued in the Optimam polyurethane implant until 1991.
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From page 67... ...
These changes and the addition of barrier layers and other shell changes may result in some different molecular species in gel fluid diffusion, although the fluid itself, at least in the case of Dow Corning, is said to have remained the same since 1975. Various catalysts have also been used as the manufacturing process has changed over time.
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From page 68... ...
Tests of Surgitek, McGhan, and Dow Corning products have been reported. These reports and more generic reviews indicate that silicone gel breast implants should have no more clinically significant effect on radiation therapy than an equivalent amount of breast tissue or saline.
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From page 69... ...
. Presumably, gel, saline, or other filler, smooth or textured surface, barrier layer or standard elastomer shell, elastomer shell thickness, physical or chemical characteristics, other physical and chemical gel and gel fluid characteristics and compositions, and the presence and concentration of nonsilicone substances (e.g., catalysts or other substances remaining in the implant from the manufacturing process)
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From page 70... ...
The fumed silica or silica aerogel content of these elastomers varied from about 24 to 37%. In 1981, a 0.010-mm fluorosilicone barrier layer was added to the interior walls of implant shells filled with silicone gel.
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From page 71... ...
Data on shell thickness and gel characteristics were not made available by the company. Dorne reported weightaverage gel molecular weights of 83,500 from a model 2000 (supposedly mid-1970s)
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From page 72... ...
models of Siltex expander-implants and contoured saline implants with various valves were introduced. The elastomer from these models was used for immune adjuvant studies reported in 1996 (Hill et al., 1996~.
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From page 73... ...
Its implants have been sold in the United States and worldwide under the McGhan brand name. In 1975 the product line included smooth, singlelumen saline implants and expanders, single-lumen gel implants and combination gel-saline implants, and the first double-lumen implants (Hartley, 1976~.
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From page 74... ...
The Intrashiel shell was the subject of an experimental study in rabbits reported in the medical literature and appeared to control silicone gel fluid diffusion from implants (Rudolph and Abraham, 1980~. New shells were used on all models (except triple lumen)
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From page 75... ...
Preliminary data suggest that the barrier shells reduce gel fluid diffusion by at least an order of magnitude compared with a McGhan nonbarrier shell (Eschbach and Schulz, 1994 redacted)
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From page 76... ...
. The PVP used was low molecular weight (average molecular weight = 13,700; Beisang and Geise, 1991)
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From page 77... ...
It is not clear what chemical changes made these shells high performance, although the performance referred to was greater resistance to tearing. Barrier coating, low silicone gel fluid diffusion features were added on various lines between about 1977 and
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From page 78... ...
and a number of lesser variations in breast implant manufacture. In the first era, dominated by Dow Corning, there were thick-shell, thick-gel, patched, smooth-surfaced implants with low rupture rates, high contracture, and probably moderate to high gel fluid diffusion rates; in the second era, thin-shell, compliant gel, smooth-surfaced gel and HTV saline implants with high rupture and deflation rates, high contracture, and high gel fluid diffusion rates; and in the third era, stronger-shell, barrierlayer, compliant gel, textured gel- and saline-filled and stronger RTV saline implants with as-yet incomplete data, but presumably lower rupture and deflation rates (although not enough time has elapsed to predict this with confidence)
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From page 79... ...
IMPLANT CATALOGUE 79 tient health. Moreover, as noted in Chapter 5, it would be desirable to accumulate information on the safety, complications, and health effects of a stable group of implants and not make changes until the safety, complications, and health implications of these changes are known.
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