Bone grafting is a means to preserve bone or regenerate bone that has been lost over time. There are many terms under bone grafting ranging and the simplest is socket preservation. The best time to preserve bone is right after the tooth is removed/extracted through a procedure called socket preservation.
Socket preservation is also the cheapest and very effective at preserving the bone that is present. About 40 (forty) percent of bone is lost if the socket is not filled with a replacement graft.
Think of backfilling a hole after you dig out an area of your garden. Basically, we backfill the extraction site with the following alternatives: autograft, your bone; allograft, sterilized human bone; or alloplast, synthetic bone. By filling up the extraction site, we can preserve up to 95 (ninety-five) percent of the bone following tooth removal.