There are three basic types of bone grafts used in the oral cavity: autogenous (harvested from the patient), an allograft (obtained from a bone bank, usually from a cadaver), or synthetic (hydroxyapatite or other biocompatible substances). Grafts are primarily used for increasing the amount of bone needed for dental implants. The grafted material eventually is totally resorbed but provides a matrix or lattice-work on which new bone will grow.