The two main types of breast implants in use today are silicone or saline, both with outer silicone elastomer shells. Saline has been used predominantly in the United States because of the silicone controversy of the early 1990s and the moratorium on the use of silicone implants between 1992 and 2006. In Europe and the rest of the world, the vast majority of implants used have been silicone, as they are generally regarded as superior in terms of feel and durability. Changes in the gel fill of
modern implants have led to the development of form-stable gels that are highly cohesive through increased cross-linking of silicone.

In 1992, silicone implants were effectively removed from use other than for reconstructive or revision purposes in a trial setting. The silicone controversy arose as a series of high-profile media cases alluded to complications following breast augmentation with silicone implants. The complications reported were largely alleged systemic autoimmune diseases; however, extensive population studies worldwide since have failed to prove any link between silicone implants and any autoimmune or other disease process. The silicone implants were available for reconstruction and revision/replacement subsequently as multiple U.S. Food and Drug Administration clinical trials were developed. After U.S. Food and Drug Administration panel hearings and multiple other hurdles, the implants were approved again for general use in 2006. Ongoing U.S. Food and Drug Administration core group studies by Allergan Medical and Mentor continue to collect data for a 10-year span,¹⁰ and new data are being collected in postapproval studies that were required by the U.S. Food and Drug Administration.

Interestingly, in the recent U.S. Food and Drug Administration silicone breast implant follow-up panel in August of 2011, there were still questions raised by anti-implant groups and individuals citing anecdotal reports of autoimmune diseases caused by breast implants. Despite over 25 high-level scientific studies and over 10 meta-analyses, all of which demonstrate no link between breast implants and any autoimmune disease, there curiously remains a question of this association.¹¹–¹⁸ With the degree of science currently available, it would be difficult to conceive of what other evidence could be added to answer this question in the eyes of some individuals.

Nevertheless, the silicone moratorium in the United States prompted the widespread use of saline implants not seen in other parts of the world where silicone had not been banned. Saline has long been seen as second choice to silicone because of problems with deflation and underfilling and overfilling, giving rise to unnatural feel and texture.

Other implant types emerged as alternatives to silicone as a result of the silicone scare. These include Trilucent (soybean oil) implants, marketed as unique because of their “natural” composition and radiographic translucency.¹⁹–²² These were withdrawn because of elevated carcinogenic levels in the breakdown product of the soya. Hydrogel implants, also came and went rapidly because of the inability to demonstrate safety data.²³

The main advances in implant technology have consisted of changes to both the shell and the silicone gel. The features of most modern shells lie in their barrier layer technology and surface texturing options. The barrier layer has reduced significantly the high incidence of silicone bleeding seen in earlier generation implants.²⁴,²⁵ The surface texturing has minimized implant rotation in anatomical implants.

The gel has become progressively more cohesive through more extensive crosslinking of the silicone polymer. Cohesive gels are referred to as form stable (i.e., able to maintain their shape without collapsing under their normal weight or being deformed by the surrounding soft-tissue envelope). There is some evidence that form stability has some long-term advantages in minimizing implant-related complications.²⁸–³⁰

Essentially, there are two types of implant shell: smooth and textured. Textured devices were originally developed to mimic the surface of polyurethane implants that had a rough porous surface and were known to have very low capsular contracture rates of approximately 1 to 2 percent³¹; however, level I studies have not supported the lower capsular contracture rates in textured implants.²⁶,³²–⁴⁴ In fact, there are as many level I studies showing no difference as there are that show a benefit, likely indicating that surface texture does not have a role in capsular contracture, especially in the subpectoral pocket plane. The studies
are less conclusive for subglandular pocket plane, with a possible benefit of texture in this position.²⁷,³⁴,³⁹,⁴⁰ Coming full circle, the contracture benefit seen with polyurethane implants was most likely a biochemical effect not attributable to the surface texture. The current generation implant shells are much more durable, and the introduction of barrier layers has reduced the incidence of gel bleed significantly, a problem so often associated with early generation prostheses.

Implants are either round or anatomical. There is a wide variety within these shapes. Most round implants come in different projections for a given volume, allowing for better customization.

Anatomical implants come with even more variability of dimension because of their naturally asymmetric shape. Therefore, width, height, and projection can all be varied to optimally select a “best fit” implant.

There is much debate as to the relative merits of using round over anatomical devices and vice versa. Many surgeons will tend to use one form over the other out of habit and familiarization with a particular product. Our view is that surgeons should be comfortable in moving from one form to the other according to patient desire and the anatomy of the individual. Some situations will dictate a preference for anatomical and others for round.

Indications for round implants include the following (Fig. 1):

Indications for anatomical implants include the following (Fig. 2):