Evaluation of bone healing in patients with bone grafts and endosseous implants using single photon emission...

The aim of the present study was to evaluate the healing of onlay grafts to edentulous jaws in conjunction with osseointegrated implants using single photon emission computed tomography (SPECT). In all, 24 patients were examined who had received 26 full arch onlay grafts for augmentation of extremely atrophic edentulous jaws with secondary placement of implants 21.4 weeks after grafting. 99m-technetium-MDP scintigrams were performed immediately after grafting, before implant placement, after implant placement and before abutment connection. Tracer accumulation was assessed semiquantitatively by calculating ratios of count densities between the uptake over the calvarium and over the grafted jaws based on 16 regions of interest in the reconstructed tomograms corresponding to 16 possible areas of implant placement. 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 3 patients, infection and partial necrosis of the grafted bone occurred. In these cases, tracer uptake in areas of subsequent graft infection immediately after grafting was significantly lower compared to patients with uneventful healing as a sign of inferior graft revascularization. In 3 patients, 14 implants failed due to mobility at the time of abutment connection or loss of osseointegration within the first weeks thereafter. Significantly lower levels of tracer uptake immediately after grafting and during graft healing were found in these areas, representing a lack of bone turnover due to decreased revascularization. These areas also showed a lower increase in tracer accumulation after implant placement due to the inferior graft quality, followed by a significant increase of peri-implant bone turnover at the time of abutment connection representing inflammatory peri-implant bone reaction.