The Use of Cancellous Block Allografts for Reconstruction and Following Implant Failure Associated with Severe Bone Loss: A Prospective Survival and Histomorphometric Study.

A failed implant site is prone to reduced alveolar bone volume, both horizontally and vertically. The present study assessed the outcome of using cancellous bone block allografts for ridge reconstruction following the removal of failed implants associated with severe bone loss. Individuals presenting with failed implants and massive bone loss were included. Cancellous bone block allografts were used for reconstruction of the atrophic alveolar ridge. Radiographic evaluation at 6 months postgrafting revealed favorable bone healing, allowing implant placement. Bone biopsy samples were taken during implant placement. Twenty-four blocks and 58 implants were placed in 16 patients. Over a mean follow-up time of 40 +/- 15 months, the mean bone gain was 5 +/- 0.5 mm horizontally and 7 +/- 0.5 mm vertically. Block and implant survival rates were 96% (1 block failed) and 95% (3 implants failed), respectively. Histomorphometrically, the mean percentage of newly formed bone was 40%, with 20% residual cancellous block allograft and 40% marrow and connective tissue. Cancellous bone block allograft is a viable treatment alternative for reconstructing the alveolar ridge to achieve a successful second reimplantation, even in the presence of initial severe bone loss.