Histological analysis and gene expression profile following augmentation of the anterior maxilla using rhBMP‐2/ACS versus autogenous bone graft

Abstract Aim The objective of this report was to present histological characteristics and gene expression profile of newly formed bone following horizontal augmentation of the atrophic anterior maxilla using recombinant human bone morphogenetic protein‐2 in an absorbable collagen sponge carrier (rh BMP ‐2/ ACS ) versus an autogenous bone graft ( ABG ). Methods Bone core biopsies from 24 subjects participating in a randomized clinical trial were obtained at dental implant placement, 6 months following alveolar ridge augmentation using rh BMP ‐2/ ACS (rh BMP ‐2 at 1.5 mg/ml; total dose 4.2 mg) or a particulate ABG harvested from the mandibular retro‐molar region. A titanium mesh was used to provide wound stability and space for bone formation. Analysis included histological/histometric observations and gene expression profile of the newly formed bone. Results rh BMP ‐2/ ACS yielded bone marrow rich in capillaries, undifferentiated cells and bone lining cells compared with the ABG ( p = 0.002). Whereas no significant differences were observed in total bone fraction ( p = 0.53), non‐vital bone particles trapped in lamellar vital bone were observed in the ABG group ( p < 0.001). Real‐time PCR showed greater BMP ‐2 and RUNX 2 expression for rh BMP ‐2/ ACS over the ABG ( p = 0.001 and 0.0021, respectively), while the ABG exhibited greater expression of RANKL : OPG , BSP and OPN over rh BMP ‐2/ ACS ( p = 0.01, 0.005 and 0.0009, respectively). Conclusions Our observations suggest that formative biological processes explain bone formation following implantation of rh BMP ‐2/ ACS , whereas remodelling, resorptive/formative processes, characterizes sites receiving ABG s.