Multiple Failed Bone Grafts

Yvette, a dental implant patient from New Jersey, asks us:
My periodontist suggested to have a bone graft done before any dental implant placement. When I went back after 4 months, he told me that I lost a lot of bone after he was doing some drilling, and that he has to do another bone graft.

Another six months went by and I went back again. Finally he was able to insert the screw. He then asked me to come back in two weeks for the temporary crown. However, when i came back, he told me that the screw was a little bit loose that he has to do another bone graft for the 3rd time. I took all the necessary precautions such as eating soft food, no pressure on the site etc. Why does the bone graft keep failing? What are the chances of this 3rd bone graft being a success? What should I be asking my periodontist? Thanks for any help.