What happens to my natural breast tissue during the procedure of Breast Augmentation?

I would suspect that your implants were placed in the submuscular plane, since your breast augmentation was done only 6 years ago, and with "AA or less" natural breast tissue there would have been too much implant edge or ripple visibility with above-the-muscle placement.Since the ribcage and overlying muscles, breast, fat, and skin are all living tissues (including the bones), these tissues do respond to the pressure of implants, But you received 300cc implants, which are not huge, and I suspect that your own natural breast tissue compression, ribcage flattening, and skin stretch are not all that significant.Implants are inert devices that neither destroy nor "eat" tissue. Your body will form a scar (capsule) around any foreign body, whether it is a breast implant, pacemaker, artificial hip, earring, or grain of gravel from a fall.Explantation is always possible and fairly easy, but you will not look like you did before you received your implants. See one or more ABPS-certified plastic surgeons to discuss your present concerns and talk about the pros and cons of implant removal and the likely cosmetic implications. Best wishes! Dr. Tholen

The implants sit in a space typically being the muscle.  The muscle/breast/skin interface remains normal.  The implants do not destroy the breast tissue.  

Your breast tissue retains the ability to grow, decrase, ache, produce milk and develop any disease, all normal and the same than preoperatively.

Thanks for your question. After an augmentation the breast tissue can thin out due to the pressure effect from the implant. The tissue is not destroyed, but just compressed and thinned out by the implant, which is permanent. Most patients after explantation have a somewhat smaller volume. I would recommend an examination and consultation with a plastic surgeon in order to estimate your result after implant removal. 

Breast implants put compression on overlying breasts.  This causes thinning of breast tissues.  There is also stretching of skin.  After a few years this effect is stabilized since implants are now comfortably in place.  Some atrophy reverses after implants are removed and some does not.