In the late 1940s, a family of silicon-based polymers (plastics) was developed.
These polymers had a molecular structure of silicon and oxygen atoms with various organic sidechains, which could be varied to make the silicones liquid or solid for use as lubricants, gels, flexible sheeting or solid blocks of low reactivity and great permanency.
Silicones were rapidly taken up by surgeons as a compatible material for implanting into the human body.

Breast augmentation was first performed by injecting paraffin wax into the breast and, in 1949, by the implantation of polyvinyl alcohol sponge.
As these implants set like a rock after several years, injectable liquid silicone was tried in Asian countries (it was never legal in Australia).
However, this produced granulomas with hard lumps and opacities which precluded mammographic detection of breast cancer.

Silicone gel-filled prostheses were first used in 1964 and it has been estimated that about two million have been implanted over 30 years worldwide.
The prostheses have been modified to include fixation patches, thinner outer envelopes of silicone, silicone cores with outer envelopes of saline, and textured outer envelopes. 

Silicones are currently used not only in gel-filled breast implants, but also in ventriculocaval shunts, artificial joints and tendon sheaths, intraocular lenses, cochlear implants, as well as implantable pumps, pacemakers and defibrillators.

Problems with silicone gel breast implants

Mechanical problems

  • The fibrous tissue "capsule" that naturally forms around the implant can contract, increasing tension in the prosthesis and causing pain, hardening and changes in breast appearance.
  • Sometimes "bleeding" of silicone gel into the space between the envelope and the capsule occurs with an apparently intact envelope.
  • External trauma can rupture the implant, causing leakage of silicone gel into the capsule or migration of silicone to other body tissues.
  • The prosthesis may cause local infection.
A  study reported that 10% of prostheses needed replacement and, of these, 85% were intact and 15% had bled or had ruptured (i.e., only 1.5% of all prostheses had bled or leaked and 98.5% were intact)