Silicon substituted hydroxyapatites. A method to upgrade calcium phosphate based implants

Silicon substituted hydroxyapatites (SiHA) are among the most interesting bioceramics in the field of bioactive bone implants. Silicon incorporation into the apatite structure results in materials with comparable biocompatibility and mechanical properties, but with improved bioactive behaviour. The higher bioactivity promotes the reaction between bone and implant, leading to excellent osteointegration and ensuring the implant success. The improved properties of SiHA compared to pure HA have been demonstrated by both in vitro and in vivo tests. In this feature article, the main synthesis methods and results are reviewed for different SiHA. Finally, the role of Si is considered from the point of view of materials science at the crystallographic, micro structural and surface chemistry levels.