Histomorphometric and micro-CT analyses of calvarial bone grafts used to reconstruct the extremely atrophied maxilla

Background Calvarial bone grafts are successful in the reconstruction of the severely atrophied maxilla as a pre-implant procedure. However, not much is known about graft incorporation at the microscopic level. Purpose This study aimed to assess calvarial bone conversion 4 months after being grafted in the edentulous maxillary bone. Materials and methods In 13 patients (age:65.3 +/- 8.7 years) the atrophic maxilla was reconstructed with autologous calvarial bone. Biopsies were taken from fresh calvarial bone grafts and from the reconstructed maxillae after 4 months of healing. Micro-CT, histomorphometric, and histological analysis were performed. From three patients biopsies were obtained after 9, 11, or 45 months. Results The micro-CT analysis revealed that in the maxilla the calvarial bone was well preserved even after 45 months. Histology showed progressive incorporation of grafted bone within a maxillary bone. Osteoid and osteocytes were present in all biopsies indicating new bone formation and vital bone. Histomorphometrically, the percentage of grafted bone volume over total volume decreased from 79.8% (IQR78.7-83.3) in fresh calvarial grafts to 59.3% (IQR44.8-64.6) in healed grafts. The biopsies were taken after 9, 11, and 45 months showed similar values. Conclusions Calvarial bone grafts result in stable and viable bone, good incorporation into native maxillary bone, and a minor decrease in bone volume after healing. Consequently, they provide a solid base for implant placement in severely atrophied edentulous maxillary bone.