Effectiveness of xenogeneic and synthetic bone-block substitute materials with/without recombinant human bone morphogenetic protein-2: A preclinical study using a rabbit calvarium model

Aim: To investigate new bone (NB) formation by using bone-block substitute materials with/without recombinant human bone morphogenetic protein-2 (rhBMP-2). Materials and Methods: Three synthetic bone-block substitute materials [biphasic calcium phosphate (BCP); nanostructured hydroxyapatite (NH); 3D-printed tricalcium phosphate/hydroxyapatite (3DP)] and one xenogeneic deproteinized bovine bone mineral (DBBM) block substitute were affixed to rabbit calvarium using osteosynthesis screws, either with rhBMP-2 (n = 12) or without rhBMP-2 (n = 16). At 2 or 12 weeks (n = 6 with rhBMP-2 and n = 8 without rhBMP-2 for each week), histologic, histomorphometric and microcomputed tomography analyses were performed. Results: The application of rhBMP-2 increased NB formation in all experimental groups at both weeks. DBBM resulted in a greater area of NB compared with synthetic blocks either with or without rhBMP-2 at 2 weeks (2.8 ± 0.9 vs. 1.4 ± 0.5–1.9 ± 1.4 mm²; 1.4 ± 1.0 vs. 0.6 ± 0.3–0.9 ± 0.5 mm²) and without rhBMP-2 at 12 weeks (3.0 ± 0.8 vs. 1.7 ± 0.7–2.6 ± 1.5 mm²) (p > 0.05). NB formation did not differ significantly for DBBM and the three types of synthetic block with rhBMP-2 at 12 weeks (4.5 ± 2.0 vs. 3.8 ± 0.7–5.1 ± 1.1 mm²; p > 0.05). Conclusions: rhBMP-2 enhanced NB in all blocks. DBBM blocks yielded more NB than synthetic blocks without rhBMP-2. The application of rhBMP-2 appears to compensate for differences in late healing.