Are "gummy bear" implants better?
There is a lot of confusion about the potential benefits of "gummy bear" implants, also known as cohesive implants, but most correctly called "form-stable" silicone implants (Allergan Style 410, Mentor CPG, and Sientra). These have been in use around the world for several years but only became available in the U.S. in 2012-2013. In order to understand the role of shaped implants, we need a little history: a while back, implants with a "teardrop" profile were introduced because that was believed to create a more natural shape. However, it was later shown that the round implants actually had the exact same profile in the upright position. Round implants, on the other hand, "behave" more like a natural breast and so become the most popular choice.
But there remained a concern about silicone gel leakage; what happens when the implant ruptures? The answer is basically nothing. That is because gel is a semi-solid, not a liquid. In scientific words, it is cohesive. The newer implants were called "gummy bear" implants, used that term to emphasize that the silicone is highly cohesive, meaning that you could slice into it like gelatin and it holds its form. (Hence the correct term "form-stable.") But the softer gel in round implants is also cohesive, just softer, so it may very well continue to be the more natural-feeling implant. And the form-stable implants have a further disadvantage of requiring a larger incision for insertion, so there is a longer scar.
But because form-stable implants are shaped, not round, they provide an option where the foundation of the breast aren't round. They provide a choice where the round implants may just not fit the size and projection that the patient wants. Bottom line is for a more natural result, you need to take into account your goals as well as the limitations of your existing anatomy, not make a choice based only on the features of the implant.