Currently, a woman has to be at least 22 years old to get a breast augmentation using silicone implants. One of the main reasons is that they were only studied on women who were at least 22 years old. There is very little difference between an 18 year old woman's body, and a 22 year old women's body.
Many women who are under the age of 22, who want silicone implants travel to other countries, such as Thailand, Brazil, Bolivia, Mexico, etc. to get a breast augmentation done with silicone implants. This often leads to botched surgeries or complications with the surgery that are harmful, and sometimes fatal to these women.
Many women prefer the silicone implants because they feel more like real breast tissue, as well as act more like real breast tissue.