History of Cohesive Breast Implants

These implants were originally invented with two purposes in mind: 1) to make a longer- lasting implant, and 2) to make an implant that would maintain a more attractive and predictable shape. This goal is primarily achieved by making the gel more cohesive, so that it is less liquid-like and more solid than other silicone gel implants. For this reason, they have been known as the "gummy bear implants" Though preliminary data suggests these implants might be meeting its goals, prospective enrollees must understand that these claims have not yet been proven.

Three companies are currently doing clinical trials in the United States: Inamed, Mentor, and Silimed. Each company's devices are based upon similar concepts, but there are very significant differences between them.

Some women consider this an opportunity to have a chance to be the first to get what may be the implant of the future, while other women feel uncomfortable being a participant in a study of a new medical device. Only women highly motivated to receive these implants, and who are willing to participate in the study for 10 years of follow-up, should consider these devices.

The female breast has long been an object of both individual and societal interest. The breast represents a woman’s femininity and sensuality. One does not have to look far in the media to recognize the relative value of the breast in female perception by society. These factors represent some of the underlying motives that have made surgery of the female breast, both aesthetic and reconstructive, an area of great interest and formidable challenge to plastic surgeons for decades. Arguably no device or single surgical procedure has altered the landscape of breast surgery as dramatically as prosthetic breast implants. Breast implants have been in use for over 40 years, yet the topic still produces heated debate and emotions. On the surface it seems odd that a device that has been in use for over 40 years is still fighting for FDA approval. This review will include 2 parts and will help to outline the past development of breast implants and their present and future status.

The building block of the breast implant is based on silicone science and the biochemical principles are essential for developing implant technology. Silicone refers to a group of polymers, based upon the element silicon. Sand (Silicon dioxide (Sio2)) is one of the most abundant compounds on earth. The polymer utilized medically is poly-dimethylsiloxane (PDMS).

Silicones were first widely utilized in the World War II era for industrial and military application. Medical applications for silicone were quickly identified and silicone products are commonplace within the medical industry today. Common silicone containing products include indwelling catheters, extended wear contact lenses, pacemakers, syringes, and pharmaceuticals. Silicone products include industrial and medical grade materials. Medical grade refers to material that is pure and consistent in composition. Silicone is classified as a medical device meaning that silicone does not achieve its primary intended purpose by chemical action or through its metabolism. Characteristics of silicone that are favorable for medical uses include thermal and oxidative stability; chemical and biological inertness; hydrophobic nature; and sterilization capability.

Silicone polymers may be produced in a variety of forms including oil, gels, or elastomers (rubber). The physical state is determined by the degree of chemical cross-linking. Cross-linking occurs between vinyl and hydrogen groups on silicon atoms. Silicone oils are straight chains of PDMS without cross-linking and are insoluble in water. PDMS will remain in liquid form indefinitely. Silicone gels consist of cross-linked (of various degree) PDMS chains together with variable amounts of PDMS liquid. It is important to keep in mind that the majority of silicone gel is silicone oil within the confines set by the PDMS gel matrix. The ratio of silicone liquid to gel is controlled by manufactures to control the viscosity of the gel. Elastomers of silicone have high degrees of cross-linking and almost no PDMS oil. Breast implant shells, both silicone and saline filled, consist of a vulcanized silicone elastomer that is reinforced with silica for increased strength.1 In an effort to reduce gel bleed from silicone filled devices, phenyl or triflouropropyl groups are bonded to the shell to decrease the shell permeability to PDMS oil.2,3 These “low bleed” implant shells with “barrier coating” are characteristic of current 3rd ,4th and 5th generation implants