I currently have 700cc and 750cc implants. Should I get 550cc or 450cc for my revision? (Photo)

You would be more comfortable with 450 cc implants than with 550 cc's. However, you may have extra skin to deal with. You might even consider splitting the difference with 500 cc implants, however, these are still considered to be large implants.

The correct volume for your breast revision depends on a number of different factors, including your chest width. Using an appropriately sized implant is important to avoid distorting the shape of the breast. Respecting they width (within reason) and then modifying the projection of the implant to further change implant volume is the best option.
Whether or not a 450 implant a good option for you partly depending on the width of this implant, as well as the width of your breast 'footprint".

You have been over augmented and the volume is much too great. I would recommend explantation and lift using The Bellesoma Method. The implants are removed, your breast tissue is reshaped creating upper pole fullness, elevated higher on the chest wall and more medial to increase your cleavage. Vertical scars are avoided, nipple sensation (in 95%) and the ability to breast feed are maintained if not injured during your previous surgery. Later, fat transfers can be performed if additional volume is desired.

Best Wishes,

Gary Horndeski, M.D.