I can understand why you are confused. Sientra uses their High Strength Cohesive (HSC) in their round implants. It is a fifth generation gel. Allergen and Mentor use a slightly less cohesive fourth generation gel in their round implants. However, they are still excellent implants and widely used. Sientra's shaped implants are filled with a slightly more cohesive gel they call HSC+ which is still a fifth generation gel. Mentor and Allergan use fifth generation gel in all their shaped implants as well. All three companies use silastic shells of comparable strength all of which are felt to be very low bleed when tested. Knowing exactly if an implant is leaking once it's in your body can really only be determined by taking out the implant and looking at it. MRI scans are helpful in larger ruptures, but even they are not 100% accurate. So there is no study that can accurately measure the true rate of leakage. We do know that if the implants do leak they do not lead to alleged autoimmune diseases. Hope this helps.
What's the difference between HSC and HSC+ gel filling of the Sientra implant?
Thank you for your excellent question. The Sientra shaped implants are filled with HSC+ gel, which is slightly more cohesive than the round Sientra implants. I feel that the Sientra implants, both styles, are slightly more cohesive than Natrelle, i.e. they are a little more "gummy" feeling. Choosing between the two is largely up to patient preference, guided by the information supplied by your plastic surgeon. Both outer shells are similar, and current silicone implants are all very resistant to silicone seepage due to the cohesiveness of the gel.
Sientra High-Strength Cohesive (HSC) vs. HSC Plus
The difference between the Sientra High-Strength Cohesive (HSC) vs. HSC Plus are that in the textured and especially, because they are shaped, the "Plus" means that they are little stiffer (harder) than the regular HSC. This is to help them maintain there shape!
All silicone gel used in breast implants is cohesive
The term "cohesive" means that the gel holds together as a semi-solid, so more cohesive doesn't necessarily mean better or safer. Shaped implants have a higher degree of cohesivity because they have to be firmer in order to hold the shape. Softer gels are used in round implants and may feel more natural. I use shaped implants (also called form-stable) in about 15% of cases where the patient's anatomy is such that this type of implant fits better.