Why can't you get silicone breast implants bigger than 800cc but you can get saline breast implants that are much bigger?

Silicone implants come with a fixed volume.  Saline implants have volume ranges. So they can be overfill. The FDA mandates and makes these rules. The heavier than the implant the more likely it is to cause changes in the skin due to stretching and possibly exposure of the implant.

Currently, the largest size implants that the FDA has approved is 800cc.  Silicone implants are pre filled to the specified volumes.  Saline implants are empty at the time of manufacturing and are filled during surgery with salt water.  There are no larger silicone implants available, but I ask for them all the time and the manufacturing companies are supposedly working on them.  An 800cc saline implant can be over filled (off label) to any volume, which is how saline implants can be much larger.

I'm not sure why anyone would want breast implants larger than 800 mL. The largest standard volume is 100 mL but custom implants can be made. Saline implants can be overinflated but the appearance And artificial feel would be a significant aesthetic issue in this circumstance.

Good question! I have asked our local reps. the same question as I sometimes find a need for a large size with my breast cancer reconstruction patients.  They say that several other surgeons have asked for 900 cc ++ implants but currently only saline implants will go that high.  Perhaps it is an issue with biomechanics and the design of the implant or perhaps there is not enough demand.

Mentor, Alleragan and Sientra do not manufacture gel  implant larger than 800 cc.  A saline implant can be over expanded but will be very round, tight and can flip upside down in the breast capsule.  

Because unfilled aline implants are manufactured easier than pre filled silicone implants. You can have special order silicone but the cost is over $2,000+++. 

The implants are approved by the FDA for use individually. In other words, only the implants they have are approved. The largest volume gel in the US is 800cc. They are prefilled with the gel and fixed in dimension and volume. The 800 cc saline on the other hand, is filled at the time of surgery and has a WIDE range of volume that can be placed, though the manufacturer's recommendations are rather narrow in scope. I do a lot of large implants and it is not uncommen to fill to 1200 -1400-1800 ccs. There used to be custom implants available in the US, but not any more.