A breast implant is a prosthesis used in cosmetic surgery to enhance the size and shape of one's breasts or to reconstruct the breast (for example, after a mastectomy, or during male-to-female sex reassignment surgery). There are three types of breast implants: *Saline-filled which have an external silicone shell and are filled with sterile saline liquid. These implants are currently the only ones available in the United States.
Definition from en.wikipedia.org/wiki/Breast_augmentation