Tissue-Engineered Bone Construct Promotes Early Osseointegration of Implants with Low Primary Stability in oversized osteotomy

Abstract

Abstract Objectives To evaluate the histological parameters and bone mechanical properties around implants with low primary stability (PS) in grafted bone substitutes within an oversized osteotomy. Materials and Methods An oversized osteotomy penetrating the double cortical bone layers was made on both femora of 24 New Zealand white rabbits. Bilaterally in the femur of all animals, 48 implants were installed, subdivided into four groups, corresponding to four prepared tissue-engineered bone grafts (TEBGs), which were placed between the implant surface and native bone wall: A: tricalcium phosphate β (TCP-β); B: autologous adipose derived-stem cells with TCP-β (ASCs/TCP-β); C: ASCs transfected with the enhanced-GFP gene with TCP-β (EGFP-ASCs/TCP-β); D: ASCs transfected with the BMP-2 gene with TCP-β (BMP2-ASCs/TCP-β). Trichrome fluorescent labeling was conducted. Animals were sacrificed after eight weeks. The trichromatic fluorescent labeling (%TFL), area of new bone (%NB), residual material (%RM), bone-implant contact (%BIC), and the removal torque force (RTF, N/cm) were assessed. Results The BMP-2 overexpression of ASCs sustained for ten days and greatly enhanced osteogenic differentiation. At eight weeks post-implantation, increased %NB and RTF were found in all groups. The most significant value of %TFL, %BIC and lowest %RM was detected in group D. Conclusion The low PS implants osseointegrate with considerable new bone in TEBGs peri-stuffed site. The addition of ASCs and BMP-2 further stimulated the %BIC. Bone graft offers wedging effect for the implant with low PS at placement and promotes osteogenesis on their surface in the healing period.