The aim of the present study was to evaluate the healing of onlay grafts to edentulous jaws and after tumor ablation in conjunction with osseointegrated implants using sequential bone scintigraphy and single photon emission computed tomography (SPECT). A total of 24 patients were examined after onlay grafting of extremely atrophic edentulous jaws and after tumor ablation with secondary implant placement 21.4 weeks after grafting. Technetium-99m (MDP) scintigrams were performed immediately after grafting, before and after implant placement, and before abutment connection. Tracer accumulation was assessed semiquantitatively by calculating ratios of count densities between the uptake over the calvaria and over the grafted jaws. There was a significant decrease in tracer uptake during graft healing, which was followed by a significant increase after implant placement and a subsequent decrease during implant healing. In patients with complicated healing, tracer uptake in areas of subsequent graft infection immediately after grafting was significantly lower compared with patients with uneventful healing. These areas also showed a lower increase in tracer accumulation after implant placement due to inferior graft quality, followed by a significant increase of tracer uptake at the time of abutment connection, representing inflammatory peri-implant bone reaction. Sequential bone scintigrams and bone SPECT have the prognostic potential to detect areas of inferior graft revascularization leading to graft infection or failure in the osseointegration of implants. Only bone SPECT allows an exact localization of areas with complicated healing.