Natural bone loss following tooth extraction in the upper or lower jaw often leaves inadequate bone in which to place dental implants
. To correct this problem, the gum is lifted away from the ridge to expose the bony defect and the defect is then filled with bone or bone substitute materials. A barrier membrane is then used to contain this bone graft and to prevent unwanted non-bone cells from migrating in. This helps build up the bony ridge and enables the placement of dental implants in the area. Ridge modification caused by bone grafting has been shown to greatly improve appearance and increase the chances for successful implant osseointegration. The materials used for bone grafting can either be autogenous bone (harvested from another area of the body such as the corner of the jaws or the chin) or xenografts (derived from an animal donor such as a cow) or alloplastic materials (synthetic bone graft materials) All these materials act as a scaffolding for new natural bone cells to migrate into the area and form new bone that eventually replaces the bone graft material.