Can an external tissue expander over the breasts kill fat cells?

You are mixing information about internal and external tissue expansion. Internal tissue expansion will cause some thinning of tissue over the expander (but doesn't necessarily kill fat cells). Also external expanders are only used in the setting of later fat grafting. You will not achieve any results from using the expander alone.

The Brava suction device you are referring to never worked. I put it under the category of wishful thinking. It had been tried fir years and found to be useless. I don’t believe it’s even available anymore.

Brava was conceived of and originally produced as a means of permanently enlarging the breasts by applying frequent intermittent suction to the breasts. Typically 8 hours a day for a month or more. Keep in mind, you cannot hide it under clothing. After extensive testing, average breast enlargement after using it for months at a time was less than 100 cc, or about two thirds the size of the smallest breast implant. There was no long term follow up to confirm efficacy past 6 months. One of the inventors, Roger Khuri, M.D., went on to pioneer fat transfer to the breast, incorporating the Brava system as a means of optimizing the breast tissue for fat grafting. My suggestion is either fat grafting of implant based breast augmentation. 

Dear bunni21,
it is unlikely that external tissue expander will increase the size of your breasts. The best options are breast implants and fat grafting. If you are considering a surgery, I would suggest you to consult a board-certified plastic surgeon. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

External tissue expansion devices for breasts such as the Brava system offers only modest and temporary breast augmentation. The device was originally designed to be used in conjunction with fat transfer, for which it had modest success at best. Depending on your particular situation, breast augmentation with implants or fat transfer is still the best option. Consult with a board-certified plastic surgeon  in your area to explore the best options for you. Good luck.

Most suction devices give a modest increase in size that is not always maintained. You will have more success and consistency with implants. If you overuse the suction device, you can damage fat cells.

Thank you for the question and expansion with the Brava system is meant to enhance fat survival and growth though very the changes it brings in the breast are very modest.   An augmentation with implants gives a much more reliable resultDr Corbin