Breast implant. Artwork of a silicone implant in a longitudinal section through a woman's breast. A silicone implant (blue, oval, centre) is used in cosmetic surgery to enlarge a breast (augmentation mammoplasty). Implants are also used to restore breast shape after breast tissue removal for cancer. Synthetic silicone is widely used in implants in cosmetic surgery because it is resistant to body fluids, permeable to oxygen, and is not rejected by the body. Immediate results to surgery are usually excellent, but build up of scar tissue (not seen here) around the implant makes the breast harder.