Saline implants are placed inside the breast empty and filled once they are in the desired position. Because saline implants are filled with a lighter liquid, they are more likely to ripple and/or wrinkle.
Silicone-filled breast implants are made of a cohesive silicone gel, and are smoother and softer than saline implants. Thus, silicone implants tend to look and feel more natural. Silicone implants retain their shape better, too.
A second type of silicone implant called Memory Gel is also available. This more cohesive implant does not run when cut and holds together to give the natural look of breast tissue.