The Allergan 410 and the Sientra implants are FDA approved and available; Mentor CPG is an investigational device only.

Each of the three breast implant manufacturers in the United States has its version of a highly cohesive implant.

All such implants have surpassed the rigorous standards of the FDA, all measures of these implants were superior to any other implant previously studied, including saline breast implants and the standard silicone gel breast implants that were approved in 2006.


The implants vary in their dimensions, shell, and feel. The Natrelle 410 comes in twelve shapes, Sientra five shapes, and the Mentor MemoryShape comes in six shapes. This means that for a given volume, say 300 cc, there are many implant shapes to choose from. And since these implants essentially hold their shape, they offer the possibility of improved breast enhancement.

Only several shapes are necessary for breast augmentation, the others being useful predominantly in reconstruction after mastectomy. Despite the different numbers in the range of each manufacturer, they all make implants in the size that fit all of the most common situations. So in no way should the number of available shapes affect anyone’s decision whether to have these implants. Some even think having so many shapes is even a marketing ploy.

Even in the shapes that are the most similar, each manufacturer’s implant comes in different ratios of height, width, and volume. Some have a more exaggerated teardrop shape and some are more round. Some have thinner edges and some have wider edges. Because these implants are relatively cohesive, the differences in the shape of these implants can translate into a different final appearance of the breasts.

All of the anatomic cohesive implants have texturing on the outside of the shell. This helps hold the implant in place and keeps it from moving out of position. Each manufacturer makes a case as to why their texturing is the best, but it is unclear whether one surface is any better than the others.

For instance, Mentor’s MemoryShape™ uses a texturing called Siltex®. It is a texture that is embossed on its surface. Allergan uses Biocell™, which is more of a 3D sort of architecture. Both companies produce their own data as to why they think their texturing is better.

The cohesive gel that fills the implants all have different degrees of cohesiveness. A more cohesive gel will create an implant that better holds a shape and is more resistant to shell folds, but it will feel firmer. A less cohesive gel will feel squishier, but it may not hold its shape as well and may be more prone to developing minor folds in the shell. So as you would expect, the manufacturer of the firmer gummy bear implants criticizes the competitor’s for being too soft and not holding its shape. And the manufacturer that makes the softer implant would criticize the competitor’s implant for not maintaining the shape and durability as theirs.

The implant manufacturer can also vary the volume of gel it puts inside the shell. A more filled shell may have less chance of developing a fold, but it will be firmer. Balancing the size of the shell with the amount and cohesiveness of the filler is where the art and science of breast implant manufacturing meet. Each manufacturer has its own philosophy as to how to balance these considerations.
And there are at least a dozen more important factors in the manufacturing process, all of which create minor differences in the final implant.

Given a chance to look and feel the implants, you will certainly notice a difference. But the difference in the body is not nearly as profound as it looks on a table.


A common misperception by both patients and surgeons is that Sientra makes a round form stable implant, and that is simply not true. The round Sientra implants look and feel nearly identical to the standard silicone gel implants made by Allergan and Mentor. To be considered a gummy bear, an implant must maintain a shape while still being soft. But the Sientra round implant does not maintain a shape; it is as malleable as any implant, and the gel in an upright implant distributes to the lower part of the shell the same as any other silicone implant.

There are form stable round implants, but they have never been available in the United States. The only reason a round implant can look like a breast is that gel from the upper part of the implant can slide down within the shell to add more fill to the lower pole of the implant, essentially creating a teardrop shape out of a round implant. But when a truly gummy bear filler is put in a round implant, that gel will not redistribute, and the implant will always have a very round look. These implants are only used sparingly, usually in cases of women who actually want a very round and obviously augmented breast.


Experienced surgeons will be attracted to or dissuaded by certain characteristics of an implant. They will have opinions about the ideal degree of firmness v. softness, the type of texturing, or the shape that best works for them to create beautiful breasts. Some will use different implants depending upon the anatomy or needs of a patient. All of these implants come with a very good warranty, but the implant warranties vary between the manufacturers and sometimes one may be better than the other. And though all of the implants have been shown to be safe, some surgeons prefer one company to another based upon their personal interaction with them throughout the years.


Your big decision is whether to use a standard round silicone gel implant or a teardrop shaped gummy bear implant. Once you know you want use the gummy bear, the differences are relatively minor. The only thing that will make a big difference is your surgeon. They are far more important than the implant.

These implants require more careful preoperative implant selection and more precise surgical technique. They can create astonishingly gorgeous results, but they are not for every patient – nor every surgeon. Find a surgeon who understands what you want and can explain to you what they think they will be doing. Make sure they demonstrate to you their care, understanding, and experience.

Once you select your surgeon, leave it to them to select the specific implant that they want to use. You want them to use the implant with which they are most comfortable.


One of the reasons that surgeons use gummy bear implants is to predictably shape the breast. The shape of the breast implant in this MRI demonstrates how it mostly maintains its original shape and how it then imparts that shape upon the breast.

This MRI of a standard round implant shows how it can adopt a random shape, because the non-cohesive silicone filler does not maintain any particular shape.

On the right is a round Sientra implant, an implant that some patients and surgeons consider to be form stable. On the left is a truly form stable round implant from Europe that is made with a much more cohesive silicone than even the Sientra, and it is not available in the United States.

Look what happens when the European highly cohesive round implant is turned on its side: it still looks round. There is a slight change in shape (nothing is truly form stable,) but it still looks round.

When the Sientra round implant is turned on its side, the shape is not maintained, so it is erroneous to describe it as a form stable implant. Were it to be form stable, it would feel firm and look very round, which is why round highly cohesive implants are not popular anywhere in the world.

Comparing that round form stable implant directly to a stand round silicone implant illustrates a number of important points. The round implant stays round, but avoid any folds. The standard gel implant adopts a somewhat teardrop shape, but develops folds.

On the left is a teardrop implant made with a non-cohesive silicone gel, and on the right is a Style 410 cohesive implant.

When they are turned upright the teardrop implant with the non-cohesive filler collapses and loses its shape. That’s why it only makes sense to use highly cohesive silicone gel in teardrop shaped implants.

On the left is the 410 teardrop implant, and on the right is a highly cohesive round European implant. This highlights why a form stable implant must be teardrop; if it is not, it looks too round and fake.

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