them for support and proper integration into the mouth. as mentioned earlier bone grafts come in various forms such as autologous (from the same person), allograft, xenograft (mainly bovine bone), and alloplastic materials. bone grafts can be used prior to implant placement or simultaneously. people who have been edentulous (without teeth) for a prolonged period may not have enough bone left in the necessary locations. in this case, autologous bone can be taken from the chin, from the pilot holes for the implants, or even from the iliac crest of the pelvis and inserted into the mouth underneath the new implant. alternatively, exogenous bone can be used: xenograft is the most commonly used, because it offers the advantage of exceptional volume stability over time. allograft offers the best regeneration quality but has lower volume stability. often a mix of different kinds of bone grafts is used. in general, bone graft is either used en bloc (such as from the chin or the ascending ramus area of the lower jaw) or particulated, in order to be able to adapt it better to a defect. dental bone grafting is a specialized oral surgical procedure that has been developed to reestablish lost jawbone. this loss can be a result of dental infection of abscess, periodontal disease, trauma, or the natural process of aging. there are various reasons for replacing lost bone tissue and encouraging natural bone growth, and each technique tackles jawbone defects differently. reasons that bone grafting might be needed include sinus augmentation, socket preservation, ridge augmentation, or regeneration. there is currently some evidence supporting the use of autologous platelet concentrates (cell fragments containing growth factors to promote tissue regeneration) when bone grafting is used to treat gum disease. fibular shaft another common bone graft, which is more substantial than those used for dental implants, is of the fibular shaft. after the segment of the fibular shaft has been removed normal activities such as running and jumping are permitted on the leg with the bone deficit. the grafted, vascularized fibulas have been used to restore skeletal integrity to long bones of limbs in which congenital bone defects exist and to replace segments of bone after trauma or malignant tumor invasion. the periosteum and nutrient artery are generally removed with the piece of bone so that the graft will remain alive and grow when transplanted into the new host site. once the transplanted bone is secured into its new location it generally restores blood supply to the bone in which it has been attached. other bone grafts are used in hopes that the defective bone will be healed or will regrow with little to no graft rejection. besides the main use of bone grafting – dental implants – this procedure is used to fuse joints to prevent movement, repair broken bones that have bone loss, and repair broken bone that has not yet healed. furthermore, bone grafts or substitutes are widely used for augmentation of spinal fusion procedures. risks as with any procedure, there are risks involved; these include reactions to medicine, problems breathing, bleeding, and infection. infection is reported to occur in less than 1% of cases and is curable with antibiotics. overall, patients with a preexisting illness are at a higher risk of getting an infection as opposed to those who are overall healthy. risks for grafts from the iliac crest some of the potential risks and complications of bone grafts employing the iliac crest as a donor site include: acquired bowel herniation (this becomes a risk for larger donor sites (>4 cm)). about 20 cases have been reported in the literature from 1945 until 1989 and only a few hundred cases have been reported worldwide meralgia paresthetica (injury to the lateral femoral cutaneous nerve also called bernhardt-roth's syndrome) pelvic instability fracture (extremely rare and usually with other factors) injury to the clunial nerves (this will cause posterior pelvic pain which is worsened by sitting) injury to the ilioinguinal nerve infection minor hematoma (a common occurrence) deep hematoma requiring surgical intervention seroma ureteral injury pseudoaneurysm of iliac artery (rare) tumor transplantation cosmetic defects (chiefly caused by not preserving the superior pelvic brim) chronic pain bone grafts harvested from the posterior iliac crest in general have less morbidity, but depending on the type of surgery, may require a flip while the patient is under general anesthesia. costs bone graft procedures consist of more than just the surgery itself. the complete three-month total cost of a complex posterolateral lumbar spine fusion bone graft supplemented with graft extenders ranges from a mean of approximately us$33,860 to us$37,227. this price includes all visits in and out of the hospital for three months. besides the cost of the bone graft itself (ranging from us$250 to us$900) other expenses for the procedure include: outpatient rehabilitation fees (us$5,000 to us$7,000), screws and rods (us$7,500), room and board (us$5,000), operating room (us$3,500), sterile supplies (us$1,100), physical therapy (us$1,000), surgeon's fees (average us$3,500), anesthesiologist fees (approximately us$350 to us$400 per hour), medication charges (us$1,000), and additional fees for services such as medical supplies, diagnostic procedures, equipment use fees, etc.