On healing of titanium implants in iliac crest bone grafts

Abstract: Bone grafts and titanium implants are commonly used for surgical/prosthetic rehabilitation of the atrophic edentulous maxilla. The factors which influence bone graft healing and implant integration are not sufficiently understood.The aim of this dissertation was to evaluate autogenous bone grafting and delayed placement of titanium endosteal implants for reconstruction of the atrophic maxilla, including the effects of different patient factors on bone graft healing and integration of titanium implants into grafted bone. A total of 46 patients with severe maxillary atrophy received onlay- (n=35) or interpositional bone grafts (n=11) and 6 mo. later received 341 titanium endosteal implants. All bone grafts were harvested from the iliac crest. All patients received fixed dental bridges and were followed clinically and with radiographical examinations for 3 yr.In Papers I and II, a total of 68 titanium microimplants were placed and retrieved from the bone grafts at various time points for histological analysis of the bone graft-implant interface. Integration was better after 6 mo. healing than placement in conjunction with bone grafting. Implant integration was similar for the two bone-grafting techniques.In Papers III and IV, originally including 29 patients and 222 implants, implant stability was measured with resonance frequency analysis (RFA) at placement, abutment connection, after 6 mo. of loading (III) and after 3 yr. of loading (IV). Ten non-grafted patients measured at the same time points were used as controls (III). RFA showed equal implant stability in grafted bone vs. non-grafted bone (III). Stability did not change from the 6-mo. to the 3-yr. control. Cumulative survival was 90% after 3 yr. (21 implants failed). Thirteen implants were lost prior to loading and 8 during functional loading. The group of failed implants showed a lower primary RFA stability than those that remained stable for 3 yr. All patients received and maintained a fixed dental bridge throughout the study. In Paper V, the graft volume changes (GVC) during the 6-mo. healing period prior to implant placement were studied in 30 patients using computerized tomography. Blood samples were taken from 25 patients in conjunction with bone grafting and were analysed for 13 haematological factors. Bone mineral density (BMD) was measured in 21 patients. Biopsies of the bone grafts were analysed for bone volume fraction (BVF). GVC (loss) was correlated with decreased BMD of the lumbar vertebrae L2-L4. There was no correlation between the haematological factors and GVC. Implant failure was not correlated with BMD, BVF or GVC. This dissertation shows that surgical/prosthetic rehabilitation of the atrophic edentulous maxilla with autogenous iliac crest bone grafts and delayed placement of titanium implants after 6 mo. of graft healing is effective, reproducible and functional. RFA at placement may be able to predict later implant failure.