There are four main types of bone grafting: Autograft is the bone of the patient itself. It is harvested mainly from the iliac crest or chin area. Since it contains living cells and human growth factors, it is the perfect bone replacement. Allograft bone is extracted from humans other than the individual receiving it. It can be removed from cadavers or living donors (tissue harvested from hip replacement surgery). It has the composition and structure of natural bones. Alloplast is a synthetically produced bone graft material from hydroxyapatite (a naturally occurring mineral) so that there is no chance of transmission of the disease. Calcium phosphate-based ceramics such as hydroxyapatite (HA) and tricalcium phosphate (TCP) are the most common alloplastic materials. Xenograft bone replacement originates from a non-human animal such as bovine bone (or recently porcine bone) that can be freeze-dried or demineralized and deproteinized.