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FDA Breast Implant Consumer Handbook - 2004
DEVICE DESCRIPTION
Breast implants may vary in shell surface (smooth versus textured), shape (round or shaped), profile (how far it sticks out), volume (size), and shell thickness. The primary parts of most breast implants are a shell (otherwise known as the envelope or lumen), a filler, and a patch to cover the manufacturing hole.
With respect to the shell design, while most breast implants are single lumen (just the shell), some breast implants are double lumen (one shell inside another shell). With respect to the filler, some breast implants are manufactured with a fixed volume of filler, some are filled during the operation, and some allow for adjustments of the filler volume after the operation.
It should be noted that tissue expanders, which are silicone shells filled with saline, are regulated by FDA in a different way than breast implants. This is because tissue expanders are intended for general tissue expansion for a maximum of 6 months, after which, they are to be removed. Because of this, the design specifications (e.g., thinner shell) and preclinical testing recommendations are different for tissue expanders than for breast implants. Tissue expanders are not to be confused with the third type of double lumen silicone gel-filled breast implants described in the Silicone Gel-Filled Breast Implants section below. The third type of double lumen silicone gel-filled breast implant is a permanent implant (not intended to be removed) that allows for limited tissue expansion but is regulated by FDA as a breast implant. See that section for more details.
Below is information specific to saline-filled, silicone gel-filled, and alternative breast implants.
Saline-Filled Breast Implants
The three types of saline-filled breast implants are as follows:
- One type is a single lumen implant that is filled during the operation with a fixed volume of saline through a valve. There are no adjustments of the saline volume after the operation.
- A second type is a single lumen implant that is filled during the operation with saline through a valve. This type of implant allows for adjustments of the saline volume after the operation.
- A third type is a single lumen implant that is prefilled by the manufacturer with a fixed volume of saline. There are no valves for filling during the operation or for adjustments of the saline volume after the operation.
The silicone rubber shell for a saline-filled breast implant has the following general composition:
- cured polymeric (large) silicones
- approximately 20% of finely powdered silica that is tightly bound to the silicone polymers
- small amounts of smaller silicones
- minute amounts (parts per million) of metals, including a metal catalyst (usually tin, zinc, or platinum) (A catalyst is something that causes a change in material.)
- traces of readily evaporating materials (volatiles), such as xylene and other organic compounds.
The filler is sterile saline that should conform to United States Pharmacopeia (USP) standards for Normal Physiological Saline (injection grade). 2
Silicone Gel-Filled Breast Implants
The three types of silicone gel-filled breast implants are as follows:
- One type is a single lumen implant that is prefilled by the manufacturer with a fixed volume of silicone gel.
- A second type is a double lumen implant with (1) an inner lumen prefilled by the manufacturer with a fixed volume of silicone gel and (2) an outer lumen that is filled during the operation with a fixed volume of saline through a valve.
- A third type is a double lumen implant with (1) an outer lumen prefilled by the manufacturer with a fixed volume of silicone gel and (2) an inner lumen that is filled during the operation with saline through a valve. This type of implant allows for adjustments of the saline volume after the operation.
A silicone gel-filled breast implant has a silicone rubber shell with the same general composition as shown in the Saline-Filled Breast Implants section above.
The filler is silicone gel that has the general composition of:
- cured polymeric (large) silicones
- small amounts of uncured large and smaller silicones
- minute amounts (parts per million) of metals, including a metal catalyst (usually platinum). (A catalyst is something that causes a change in material.)
Alternative Breast Implants
An alternative breast implant typically has a silicone rubber shell with a filler other than saline or silicone gel. The filler material may or may not be a gel. An alternative breast implant may also have an alternative shell other than one made from silicone rubber.
2 As a note, one concern that relates specifically to saline-filled breast implants is the potential for the saline to become contaminated (not sterile) with fungus or bacteria and then released into the woman's body if her implant ruptures/deflates or if the valve leaks. However, saline-filled implants are now generally filled from a bag and tubing rather than from an open bowl, and this procedure may reduce the risk of this complication.
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