Immunohistochemical, tomographic and histological study on onlay bone graft remodeling. Part II: calvarial bone.
OBJECTIVE
Little information is available on the molecular events that occur during graft incorporation over time. The calvarial bone (Cb) grafts have been reported to produce greater responses compared with other donor regions in maxillofacial reconstructions, but the scientific evidences for this are still lacking. The objectives of this study are (1) to study the morphological pattern of Cb onlay bone grafts and compare them with the biological events through immunohistochemical responses and (2) to establish the effects of perforations in maintaining the volume and bone density of the receptor bed.


METHODS
Sixty New Zealand White rabbits were submitted to Cb onlay bone grafts on the mandible. In 30 rabbits, the receptor bed was perforated (perforated group), while for the remaining animals the bed was kept intact (non-perforated group). Six animals from each group were sacrificed at 5, 7, 10, 20 and 60 days after surgery. Histological sections from the grafted area were prepared for immunohistochemical and histological analyses. Immuno-labeling was found for proteins Osteoprotegerin (OPG), receptor activator of nuclear factor-kappabeta ligand (RANKL), alkaline phosphatase (ALP), osteopontin (OPN), vascular endothelial growth factor (VEGF), tartrate-resistant acid phosphatase (TRAP), Type I collagen (COL I) and osteocalcin (OC). The tomography examination [computerized tomography (CT) scan] was conducted just after surgery and at the sacrifice.


RESULTS
The histological findings revealed that the perforations contributed to higher bone deposition during the initial stages at the graft-receptor bed interface, accelerating the graft incorporation process. The results of the CT scan showed lower resorption for the perforated group (P<or=0.05), and both groups showed high bone density rates at 60 days. This set of evidences is corroborated by the immunohistochemical outcomes indicating that proteins associated with revascularization and osteogenesis (VEGF, OPN, TRAP and ALP) were found in higher levels in the perforated group.


CONCLUSIONS
These findings indicate that the bone volume of calvarial grafts is better maintained when the receptor bed is perforated, probably resulting from more effective graft revascularization and greater bone deposition. The process of bone resorption peaked between 20 and 60 days post-operatively in both groups although significantly less in the perforated group.
Pedrosa
Wagner Fernandes
WF
Department of Oral and Maxillofacial Surgery and Periodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo at Ribeirão Preto, SP, Brazil.
Okamoto
Roberta
R
Faria
Paulo Esteves Pinto
PE
Arnez
Maya Fernanda Manfrin
MF
Xavier
Samuel Porfírio
SP
Salata
Luiz Antonio
LA
D000135:Acid Phosphatase / Q000502:physiology; D000469:Alkaline Phosphatase / Q000502:physiology; D000818:Animals; D001862:Bone Resorption / Q000378:metabolism; D016025:Bone Transplantation / Q000379:methods / Q000502:physiology*; D024042:Collagen Type I / Q000502:physiology; D006085:Graft Survival / Q000502:physiology*; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000502:physiology; D008297:Male; D016348:Osseointegration / Q000502:physiology*; D015675:Osteocalcin / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology*; D053495:Osteopontin / Q000502:physiology; D053244:Osteoprotegerin / Q000502:physiology; D053245:RANK Ligand / Q000502:physiology; D011817:Rabbits; D012886:Skull / Q000601:surgery*; D018709:Statistics, Nonparametric; D000071681:Tartrate-Resistant Acid Phosphatase; D014057:Tomography, X-Ray Computed; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology
D024042:Collagen Type I; D007527:Isoenzymes; D053244:Osteoprotegerin; D053245:RANK Ligand; D042461:Vascular Endothelial Growth Factor A; D015675:Osteocalcin; D053495:Osteopontin; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase