Highly dense calcium phosphate ceramics prepared by self-hydration with hollow silicon calcium additives

Abstract

Vertebral compression fractures are common nowadays. The application of calcium phosphate bone cement (CPCs) in the treatment of vertebral compression fractures is the research focus, because of its advantages of good biocompatibility, bone conductivity and injectability. However, it is still limited in the clinical application because of its poor mechanical properties. The main reason for the insufficient strength of CPC is that there are many defects inside the solidified body during the hydration reaction. Therefore, we design a kind of hollow silicon calcium additives to regulate the crystallization behavior of CPC hydration products in the self-curing process to achieve the densification of solidified bodies in the microstructure. Firstly, we plan to increase the nucleation site of hydration products during α-TCP hydration to fill structural defects by introducing hollow bioglass. Secondly, we prepare hollow calcium silicon additive by in situ mineralization which can dissolve calcium and silicon ions efficiently are used to regulate the local hydration microenvironment to reduce the crystal size and increase the number of hydration products to obtain a highly dense solidified body structure. The experimental results show that the initial hydration intensity of CPC increased from 18.36 ± 1.72 MPa to 35.37 ± 1.84 MPa, an increase of about 92.65 %. Also, the toughness of the solidified body has been greatly improved, reaching more than 200 %. After 7 days of hydration, the mechanical strength of CPC was further improved, reaching 89.39 ± 3.65 MPa. With the addition of hollow calcium silica additives, we achieved the conversion from calcium phosphate cement to the calcium phosphate ceramic. Our work provides reference value for the clinical replacement of calcium phosphate ceramic for PMMA in vertebral compression fractures.