Silicon-substituted hydroxyapatite for biomedical applications

Silicon-substituted hydroxyapatites (Si-HAps) have gained a lot of attention due to the improved bioactivity and biological responsiveness with respect to pure hydroxyapatite (HAp). This chapter presents a complete review of the Si-HAp and highlights the influence of the Si incorporation on the material characteristics and properties by describing its microstructure, sintering behavior, in vitro bioactivity, cellular response, and biomedical applications. In particular, this review starts with the description of the Si presence in the connective tissues and its influence on the bone cell metabolism. It continues through the synthesis procedures and the properties of Si-HAps in the form of powders, granules, scaffolds, and coatings. It focuses in detail on the investigation of the Si-HAps' bioactivity and biocompatibility, with an overview of the most important in vitro and in vivo studies. Finally, the last part of the chapter summarizes the documented clinical applications of Si-HAp and emphasizes some recent attempts to improve its bioactivity by designing biomimetic/smart materials based on it