There are 2 ways that you could increase breast fullness and restore lost volume, namely breast implants and fat injections.
The main advantages of breast implants are that a reliable and predictable increase in size can be achieved, in a cost-effective manner. With 3D imaging technology, the post-operative outcome can be exactly visualised, allowing the patient to select the ideal implant to achieve her desired outcome. The outcome achieved is stable and will usually last for at least 10 years. Some of the possible disadvantages of breast implants include the presence of a surgical scar, and the risks of capsular contracture (hardening), and implant leakage, requiring eventual removal or replacement of the implant.
Fat injections involve removing fat from either the tummy, thighs or buttocks by liposuction, and injecting it into the breasts. Advantages are the absence of a surgical scar, and a very soft and natural result, without any artificial material within the breast. However, this has to be weighed against the disadvantages - usually a lesser amount of enlargement is possible compared to implants, the outcome is less predictable (some of the injected fat will be absorbed), and multiple procedures may be required, making it a more expensive option.
It’s important to discuss these issues in detail with a plastic surgeon so that you will be able to make an informed decision.