Bilayer Hydroxyapatite Scaffolds for Maxillofacial Bone Tissue Engineering

Purpose: The frequency of alveolar ridge resorption and crestal bone loss emphasizes the clinical need for bone graft substitutes to improve local bone quality prior to dental implant placement. Microcomputed tomography has been extensively employed to estimate bone quality more objectively (ie, quantitatively) by relating it to architectural parameters. In the present study, the mechanical properties of open cellular fully interconnected bilayer hydroxyapatite scaffolds, which mimicked the cortical shell/trabecular core architecture of human bone, were investigated for suitability as bone graft substitutes for maxillofacial reconstruction. Materials and Methods: Hydroxyapatite scaffolds with different architectures were fabricated using polymeric template pore sizes of 450 or 340 µm for the inner trabecular cores and 200 or 250 µm for the outer cortical shells in three different core-to-shell volume ratios. The architectural and mechanical properties and fluid permeability of the scaffolds were compared to reported values for maxillofacial bone. Results: Whereas the elastic moduli of the scaffolds were comparable, their compressive strength was observed to be in the lower range of human mandibular trabecular bone. The microcomputed tomography architectural indices for the scaffolds were comparable to those of human trabecular bone at different locations in the human body, including the maxilla and mandible. Scaffold compressive strength, elastic modulus, and fluid conductance were 0.3 to 2.3 MPa, 40.9 to 668.1 MPa, and 8.8 to 49.9 × 10-10 m3s-1Pa-1, respectively. Conclusion: Open-pore bilayer scaffolds can be fabricated to exhibit sufficient mechanical integrity for maxillofacial bone graft applications to match specific bone site architecture while providing sufficient permeability to sustain bone regeneration. Keywords: alveolar resorption, architecture, bone grafts, hydroxyapatite, microcomputed tomography, scaffolds