I had the surgery on Tuesday, February 26th. Tissue from donors was used to graft onto my gum tissue. If more tissue is needed, the graft skin is taken from the top of your mouth. Apparently it is a very painful process and takes a long time to heal.
I had listed myself as a donor on my driver's license for many years. When I read the book Stiffs by Mary Roach, I decided that I did not want to be a donor after all. Roach has one chapter in which she talks about body parts being harvested. Maybe you can specify that you only want to donate vital organs and not arms and legs and skin. But the chapter was sufficient to convince me that I did not wish to be a donor.
However, I am very grateful to whoever donated tissue for my skin graft on my gums.