Low‐dose rhBMP2/7 heterodimer to reconstruct peri‐implant bone defects: a micro‐CT evaluation

Abstract

To delineate the dynamic micro-architectures of bone induced by low-dose bone morphogenetic protein (BMP)-2/7 heterodimer in peri-implant bone defects compared to BMP2 and BMP7 homodimer. Peri-implant bone defects (8mm in diameter, 4mm in depth) were created surrounding SLA-treated titanium implants (3.1mm in diameter, 10mm in length) in minipig's calvaria. We administrated collagen sponges with adsorbed low-dose (30ng/mm(3) ) BMP2/7 to treat the defects using BMP2, BMP7 or no BMP as controls.2, 3 and 6weeks after implantation, we adopted micro-computer tomography to evaluate the micro-architectures of new bone using the following parameters: relative bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), connectivity density, and structure mode index (SMI). Bone implant contact (BIC) was also revealed histologically. Consistent with 2 and 3weeks, after 6weeks post-operation, BMP2/7 resulted in significantly higher BV/TV (63.033±2.055%) and significantly lower SMI (-4.405±0.500) than BMP2 (BV/TV: 43.133±2.001%; SMI: -0.086±0.041) and BMP7 (BV/TV: 41.467±1.850%; SMI: -0.044±0.016) respectively. Significant differences were also found in Tb.N, Tb.Th and Tb.Sp at all time points. At 2weeks, BMP2/7 resulted in significantly higher BIC than the controls. Low-dose BMP2/7 heterodimer facilitated more rapid bone regeneration in better quality in peri-implant bone defects than BMP2 and BMP7 homodimers.