Use of sequential bone scintigraphy for monitoring onlay grafts to grossly atrophic jaws

Objectives: To evaluate the capability of sequential bone scintigraphy for assessing the viability of avascular onlay grafts in combination with primary or secondary implant placement. Methods: Forty-six patients with severe alveolar ridge atrophy received full-arch onlay grafts from the iliac crest. Twenty patients received primary insertion of endosseous implants, while secondary implant placement was performed in 26 patients after an average interval of 95 days. In cases of primary implant placement, bone scintigraphy was performed after grafting and before abutment connection. In patients with secondary insertion, bone scans were performed after grafting, before and after implant placement and before abutment connection. For bone scintigraphy, 8 MBq Tc-99m-MDP/kg body weight were administered intravenously and anterior views of the skull were obtained 3 h later. Regions of interest were drawn over the grafted area and over the calvarium as a reference area. Ratios of count densities between jaw and calvarium were calculated as a measure of tracer uptake. Results: Bone grafts with primary insertion of implants showed a significant decrease (P=0.0001) in ratios calculated for the whole graft from a mean of 3.53 after grafting to 2.35 before abutment connection. In cases of secondary implant placement, ratios decreased significantly after grafting from 4.04 to 2.78 before implant placement (P=0.0001). After implant placement, there was a significant increase to 3.28 (P=0.0062), which was followed again by a significant decrease to a mean ratio of 2.58 (P=0.0437). Conclusions: Sequential bone scintigrams can provide information:about the viability of the graft at the time of implant insertion and may thus indicate the ability of the grafted bone to accomplish osseointegration.