Breast Implant Generations

Modifications in the characteristics of the implant filler have also occurred. The most obvious being the change to saline-filled devices during the "implant crisis"; however, significant modifications have occurred in the silicone gel characteristics. The modifications in silicone gel technology are significant enough that many consider the modern era gels a fourth implant generation. Since 1992, due to increase demands to improve manufacturing processes, current silicone gel implants are improved devices with slightly thicker shells and more cohesive gel filler than third-generation devices.

Because breast implants are filled with medical-grade silicone, changes in silicone gel chemistry have centered on the cohesive quality of the gel. All silicone gels are cohesive but the degree of cohesiveness has clinical importance. The degree of cohesiveness is a reflection of the elastic memory or shape retention of the gel. Cohesiveness is produced by the chemical cross-linking of the silicone gel molecules. The degree of cohesiveness imparts important characteristics to the structure and feel of the implant. Second-generation implants produced before 1985 contained minimally cohesive gels. Third- and fourth-generation devices evolved to contain increasingly cohesive gels after 1985, and in 1993, form-stable cohesive gel implants were introduced.

The fifth-generation implants are form-stable cohesive gel implants (e.g., Allergan/Inamed/McGhan 410 and Mentor CPG). These are shaped silicone gel devices with enhanced cohesion that offer improved breast shaping and results. These implants are currently undergoing clinical trials in the United States. Silicone gel and saline are the only materials presently available for use as filling material for breast implants in the United States. Soy-filled implants (Trilucent) were marketed for a short time period in Europe but were voluntarily pulled from the market in 2000 by the manufacturer (15, 16). Trilucent implants contained Trilipid 6, a medicalgrade triglyceride fat extracted from soybean oil. This material was studied in animals and not shown to be a safety concern. Approximately 5,000 European women and 50 U.S. women received the implants as part of European and U.S. clinical trials. In the United States, the devices had limited availability through an investigation device exemption (IDE). The devices were taken out of clinical use due to the development of inflammatory reactions resulting from the leakage of the oil into the surrounding tissues (17, 18). The reactions resolved with removal of the devices and did not present long-term health concerns. There are presently no other alternative fillers available through clinical trial.

More Information about Cohesive Gel Implants