The aim of the study was to compare the bone mineral apposition rate (BMAR) of immediately loaded implants with an unloaded control during the early healing phase in the partially edentulous mandible. In seven mini pigs, three premolars and the first molar were removed in the left mandible. Three months later, five implants were installed. Four implants received a fixed provisional restoration and were loaded immediately. The most anterior implant was used as unloaded control. Polychromatic fluorescence labelling was performed to assess the BMAR. After 4 months, the implants were retrieved together with the adjacent bone. Histological specimens were prepared and subjected to a fluorescence microscopic and histomorphometric analysis. Two provisional restorations were found partially lost at the end of the observation period. One implant that had lost the splinting fixation showed soft connective tissue healing. The BMAR did not differ statistically significantly between loaded and unloaded implants and within the single groups during the observation period (BMARloaded days 14-42=1.8+/-0.2 microm/d, BMARloaded days 42-70=1.8+/-0.1 microm/d, BMARloaded days 70-98=1.6+/-0.1 microm/d, pBMARloaded days 14-42/42-70/70-98 =0.156, BMARunloaded days 14-42=1.7+/-0.1 microm/d, BMARunloaded days 42-70=1.8+/-0.2 microm/d, BMARunloaded days 70-98=1.6+/-0.4 microm/d, pBMARunloaded days 14-42/42-70/70-98=0.368, pBMARloaded/unloaded days 14-42=0.073, pBMARloaded/unloaded days 42-70=0.098, pBMARloaded/unloaded days 70-98=0.262). Four months after implant placement, the bone-to-implant contact was 77.8+/-17.3% for the loaded and 78.0+/-5.8% for the unloaded implants (P=0.753). Immediate loading does not affect the bone mineral apposition rate when compared with unloaded implants. Rigid splinting seems to be the crucial factor for implant success. Uncontrolled masticatory forces can cause failure after partial loss of the provisional restoration.

Screw-retained, full-arch restorations on six implants in an edentulous maxilla are a predictable and highly successful treatment concept as observed throughout this study with an observation period of 8 years of function, in particular with respect to low crestal bone loss and high patient satisfaction.

Implants used in this study had high survival and success rates after 5 years. Marginal bone was well maintained, irrespective of the loading regime.

Within the limitation of this study, restoration of the edentulous maxilla with an implant-supported fixed prosthesis represents an effective tool for rehabilitation over a period of 11 years.

The low morbidity at the donor sites and the good marginal bone stability in the reconstructed regions indicate that calvarial bone grafts represent a viable treatment alternative to grafts from the iliac crest.