Calcium-Deficient hydroxyapatite as a bone graft material: From hydrated-layer chemistry to clinical performance

Area of Science:

• Biomaterials Science
• Materials Chemistry
• Bone Tissue Engineering

Background:

• Calcium-deficient hydroxyapatite (CDHA) is a calcium phosphate biomaterial with bone mineral similarity.
• It is extensively researched as a bone graft substitute.
• Its distinct multiphasic nature (crystalline core, amorphous hydrated surface) influences properties.

Purpose of the Study:

• To provide a comprehensive analysis of CDHA's structure, composition, properties, synthesis, and biological performance.
• To clarify ambiguities regarding its solubility, resorption, and osteoinductive potential.
• To highlight the significance of the hydrated surface layer in governing CDHA's reactivity and biological response.

Main Methods:

• Review of existing literature on CDHA.
• Analysis of structural-chemical duality (crystalline core vs. hydrated surface layer).
• Examination of various synthesis routes (precipitation, hydrolysis, cementitious reactions).
• Assessment of biological performance through in vitro and in vivo studies.

Main Results:

• CDHA's properties (thermal stability, mechanical behavior, solubility, ion exchange) are governed by its dual structure.
• Synthesis methods impact morphology and clinical applicability.
• CDHA exhibits biocompatibility, osteoconductivity, and osteoinductivity.
• The hydrated surface layer plays a critical role in biological interactions.

Conclusions:

• CDHA is a promising and versatile material for bone substitution.
• Further research is needed for precise characterization and understanding of the dynamic hydrated layer.
• Harmonized terminology and rational design are crucial for next-generation bone graft substitutes.