What is the difference between silicone and saline

Very different : Saline means salt water. That's it. Silicone is a chemical compound containing silicon. When used in medicine or implants, the saline is usually either very close to the same salinity (strength) as the human body or half a percent lower (used in intravenous fluids or medicines).

In terms of breast: Implants, it's what the shells are filled up with. Saline is salt water, just like in an IV bag. Silicone gel is another fda approved filler for breast implants - and is currently the most popular one used in the usa.