Endosteal implants and iliac crest grafts to restore severely resorbed totally edentulous maxillae--a retrospective study.

Autogenous grafts in conjunction with endosteal implants may be indicated in conditions of severe atrophy of the maxilla. From July, 1984, to December, 1990, 20 severely atrophic arches were restored with iliac crest onlay block grafts, subantral augmentation, and 148 endosteal root-form implants. Twenty-one implants were placed at the same time as the graft to stabilize a corticotrabecular bone block. Two implants were lost (90% implant survival). One hundred twenty-seven implants were placed after graft maturity, and one implant was removed (99% implant survival). Thirteen fixed restorations and 7 completely implant-supported overdentures were fabricated. Follow-up evaluation of prostheses and implants ranged from 26 to 97 months. All the implants used for initial prosthesis fabrication and all initial prostheses remain in function. The advantages of implant placement after graft maturity and subantral augmentation are addressed. One year after implant placement, the amount of additional bone lost around the implants placed in grafted bone is similar to the bone loss around maxillary implants inserted into non-grafted bone.

Bone-grafting materials in implant dentistry.

There are three classes of bone-grafting materials based upon the mode of action. Autogenous bone is an organic material and forms bone by osteogenesis, osteoinduction, and osteoconduction. Allografts such as demineralized freeze-dried bone are osteoinductive and osteoconductive and may be cortical and/or trabecular in nature. Alloplasts such as hydroxyapatite and tricalcium phosphate may be synthetic or natural, vary in size, and are only osteoconductive. They can be divided into three types based upon the porosity of the product and include dense, macroporous, and microporous materials. In addition, alloplastic materials may be crystalline or amorphous. These materials have different properties and therefore indications. The use of the three classes of materials in diverse combinations depends upon the size and topography of the bony defect. Small defects or defects with four walls of host bone can be repaired with alloplasts alone or allografts in combination with alloplasts. The loss of three or more bony walls mandates the addition of autogenous bone to the graft or the use of a small pore membrane. The larger the defect, the more autogenous bone is required. The different indications of bone substitutes are discussed as to their specific applications in implant dentistry.

Autogenous bone grafts for endosteal implants--indications and failures.

The use of autogenous bone grafts (ABG) combined with endosteal implants permits to restore patients with conditions of extreme bone atrophy or with very demanding final results. The improvement of the biomechanics conditions, moment forces, C/I ratio, ridge relationship, length, diameter, number and location of the implants and esthetics improve the prognosis of the restoration. Large segments of autogenous bone is harvested from the iliac crest or cranium. Excellent autogenous membranous bone can be obtained intra-orally from the mandibular symphysis when smaller dimensions are needed. Indications for treatment with autogenous bone grafts are presented following the Misch/Judy available bone classification. In division C-w ridges, ABG improve the width of the ridge to permit the placement of root form implants. In Division C-h ridges, ABG improve the height available for implant placement, and permits to obtain a FP-1 or FP-2 result. In Division D ridges, ABG represent the treatment of choice. RP-4 restorations are encouraged. High success rates obtained by the author depend upon strict patient evaluation, treatment planning, careful placement of the minimum number of implants with the bone grafting procedure only to immobilize the grafted segment, progressive bone loading during the prosthetic phase, proper soft tissue management and sufficient number of implants for the planned prosthesis.