A xenograft is a type of bone or skin graft that is taken from a donor of another species. In comparison, an allograft is a type of bone or skin graft that is taken from a donor of the same species. An autologous bone graft (sometimes called an autograft) is a type of graft taken from the patient themselves, and an alloplastic graft is a manufactured or synthetic bone graft made from hydroxyapatite, a natural mineral and the main component of bone. In the dental field, xenografts are usually porcine or bovine, meaning they come from pigs or cows. The grafts are cleaned, sterilized, and prepared for implantation into the human body. The most common grafts to be used in the dental industry are bone grafts. If a patient has bone loss due to disease, trauma, or missing teeth, a bone graft may be necessary before placing a dental implant.