Saline implants are filled with sterile saline solution, and typically the implant is filled after it is inserted into the body during a breast augmentation. This type of implant is available to women ages 18 and older who are having the procedure. In the past, they were criticized for having an unnatural feel; however, modern surgical techniques which place the implant behind the chest muscle are helping them to feel more natural.
Silicone implants are filled with a silicone gel. This feels much more like human fat, giving the new breasts a more natural feel. They are available to women ages 22 and older.