Abstract
Calcium phosphates (CaPs) are biocompatible and biodegradable materials showing a great promise in bone regeneration as good alternative to the use of auto- and allografts to guide and support tissue regeneration in critically-sized bone defects. This can be certainly attributed to their similarity to the mineral phase of natural bone. Among CaPs, hydroxyapatite (HA) deserves a special attention as it, actually is the main inorganic component of bone tissue. This review offers a comprehensive overview of past and current trends in the use of HA as grafting material, with a focus on manufacturing strategies and their effect on the mechanical properties of the final products. Recent advances in materials processing allowed the production of HA-based grafts in different forms, thus meeting the requirements for a range of clinical applications and achieving enthusiastic results both in vitro and in vivo. Furthermore, the growing interest in the optimization of three-dimensional (3D) porous grafts, mimicking the trabecular architecture of human bone, has opened up new challenges in the development of bone-like scaffolds showing suitable mechanical performances for potential use in load bearing anatomical sites.
Highlights
A study conducted in the USA showed that in 2010 about 1.3 billion dollars were invested in calcium phosphates (CaPs)-based bone substitutes only [4]
One of the main disadvantages of wet methods is the low temperature used during preparation, which leads to the formation of CaP phases other than HA and/or traces of impurities in the crystalline structure due to ions from the aqueous solution used for the synthesis [35]
Considering all the various biomaterials currently available in bone regenerative strategies, calcium phosphates (CaPs) and, hydroxyapatite (HA), are among the most commonly-used due to their compositional and structural similarities to natural bone and teeth, as well as exceptional biocompatibility and biological behavior in contact with body fluids, which make them materials of choice for producing synthetic bone grafts to be used as an alternative to transplantation
Summary
The term “apatite” derives from the Greek for “apatáo” meaning “I am mistaken” as, in the past, it has been often confused with several other minerals such as fluorite and beryl It was first used by Werner in 1786, and includes a family of compounds with similar structure (hexagonal system, space group P63/m); the exact structure of apatites may change due to the different types of morphologies and non-stoichiometric variations that exist. In addition to the composition, the shape, size and distribution of HA crystals significantly affect the mechanical, biochemical and biological properties the material [34,35] These characteristics are dependent on the technique used for making HA powders
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