Novel analysis model for implant osseointegration using ectopic bone formation via the recombinant human bone morphogenetic protein-2/macroporous biphasic calcium phosphate block system in rats: a proof-of-concept study

Abstract

Purpose: The osseointegration around titanium mini-implants installed in macroporous biphasic calcium phosphate (MBCP) blocks was evaluated after incubation with recombinant human bone morphogenetic protein-2 (rhBMP-2) in an ectopic subcutaneous rat model. Methods: Mini-implants (phi 1.8x12 mm) were installed in MBCP blocks (bMBCPs, 4x5x15 mm) loaded with rhBMP-2 at 0.1 mg/mL, and then implanted for 8 weeks into subcutaneous pockets of male Sprague-Dawley rats (n = 10). A histomorphometric analysis was performed, and the bone-to-implant contact (BIC) and bone density were evaluated. Results: Significant osteoinductive activity was induced in the rhBMP-2/bMBCP group. The percentage of BIC was 41.23 +/- 4.13% (mean +/- standard deviation), while bone density was 33.47 +/- 5.73%. In contrast, no bone formation was observed in the bMBCP only group. Conclusions: This model represents a more standardized tool for analyzing osseointegration and bone healing along the implant surface and in bMBCPs that excludes various healing factors derived from selected animals and defect models.