I want fake looking boobs. I've already had them done twice at 21! What's the difference between silicone and saline? (Photo)

I recomment you don't use saline implants, they have multiple and serious disadvantages compared with the modern cohesive silicone gel-filled models.I recomment the macrotextured implants with maximum adherence.If you want them to look fake do use the round profile models.

You need to do careful going that large as implants that are large and heavy may overwhelm the tissues of your breast and may sag more over time. There is a certain range of sizes that will tend to work best with any one's particular anatomy. Make sure you consult with a board-certified plastic surgeon who can go over your anatomy and choose implants on the larger side that will still be safe for you in the long term while providing you the more augmented look that you are trying to achieve. Silicone and Saline implants can both create the more dramatic look you are trying to achieve depending on how they are performed. There are subtle differences in how they feel and the way they move and ripple.

Silicone breast implants are not approved for individuals under the age of 22.  So either you can choose saline or wait until you are 22 years of age.  The fda only did testing and approval on individuals of that age or above so unfortunately you are not a candidate for silicone implants at this time 

 It's possible to go to 700cc, but if you want that "stripper" look, you should go with a firmer, higher profile implant. Just understand that you'll be stretching the tissues,  speeding up sagging. The bigger implant you get, the faster you'll sag.

If you want your breast fuller and are happy with the shape of them, then an implant will be fine. Keep in mind an implant will only "fill our breast up" it will not "lift them up". They will look just like they do now, they are just bigger and fuller with an implant only. If you feel this will meet your goals, then an augmentation should be fine. If you are unhappy with the position of your breast and feel they are too low, then an implant will likely not satisfy you and you will want to consider the lift. A lift will "lift them up" and put them in a higher position, change the size of the areola and "lift" them off of your chest. Often times both of these procedures are combined to achieve an optimal result. By lifting them and adding volume, the breast will not only sit higher on your chest but will also have the nice fullness from the implant. Dr Scott Ennis

As you have already had a lift and a vertical scar that is visible you can put in larger implants at any point in time.  You can get silicone implants under the age of 22 but this is typically consider off label use.  That means that the manufacturers warranty for the implants is not valid.  It would appear that you have implants that are outside the muscle so the larger you go, the faster you will droop.  You will need to make a business decision whether you want to continue to have operations to increased size and decrease the stretch of skin.  Each time you instrument the pocket, you increase the risk of infection to the pocket and the potential for capsular tightening and hardness.  You might consider conversion to a submuscular implant which is textured to get a longer-lasting result.  One of your key words above is  silicone injection.  Those of us in plastic surgery who are  board certified will recommend strongly that you  avoid that. We see lifetime complications in girls who do this.

You cna simply increase the size and use a higher profile implant. But here is the rub, silicone, truly your best choice, is not FDA approved till you are 22. Saline will thin your breasts, cause rippling and further bottoming out, which you already have. Then there is the added weight, 450cc implants weigh a pound. In that case you would be adding 2 pounds of weight to your chest, I would suggest you consider that.Stephen M. Davis, MD, FACSGreen Hills Plastic Surgery

Just exchange to the size you desire. NO lifting operation needed. You can not base silicone til you are 22 years old... 

You can achieve the "fake" look you desire by getting larger implants and ones with a higher profile.  Saline implants would have a higher chance of showing rippilng and are not as soft as silicone.  Good luck.

You can have what you ask for, full and round "fake" looking breasts. We would discourage saline as the look you are after is best with a subglandular higher profile silicone to avoid ripple and maintain softness even with thin cover. Hope this works out for you.