Yes, it is entirely possible.
They are somewhat dangerous due to possibility of the silicone bursting and ruining the breast health. It can also hinder mammograms and not allow for the detection of breast cancer in the future.
Anna Kooiman has not publicly declared that she had breast implants although it is rumoured that she had breast implants.
No, she didn't really get breast implants
"The three main types of breast implants are those filled with silicone, saline, or gel. The best choice for you will depend on the shape, volume, and feel you are trying to achieve. It is important to note that there are also varying health risks associated with each type of implant; more information on the health risks can be found by contacting the American Food and Drug Administration, or the American Medical Association."
Breast implants.
No, Mariah Carey didn't have breast implants.
It is unknown as to whether Rhonda Vincent has breast implants.
No, breast implants have to be filled in during surgery only.
No, the breast implants themselves do not harden. The actual breasts still do. But that's of course harder to feel when they're behind breast implants.
Some risks involved in breast feeding with implants are the nipple may not be the same shape as it was prior to surgery. The feel and shape of the breast may change after breast augmentation surgery as well.
Breast implants can be inserted under or over the muscle.