The in vivo dissolution of tricalcium silicate bone cement.

This study aimed to investigate the in vivo dissolution of tricalcium silicate (Ca3 SiO5 , C3 S) bone cement in the rabbit femoral defect. Results indicated that C3 S paste directly integrated with the bone tissue without the protection of the bone-like apatite. Calcium silicate hydrate gel (C-S-H gel) and Ca(OH)2 were the main components of C3 S paste. The dissolution model of C3 S paste was a mass loss rather than a decrease in volume. The initial dissolution of C3 S paste (0 ~ 6 weeks) was greatly attributed to the release of Ca(OH)2 , and the later dissolution (>6 weeks) was attributed to the decalcification of C-S-H gel. Although the mass of C3 S paste could decrease by more than 19 wt % after 6 weeks of implantation, the created pores (<1 μm) were not large enough for the bone tissue to migrate into C3 S paste. The loss of Ca ions also resulted in the transformation of SiO4 tetrahedrons from Q1 and Q2 to Q0 , Q3 , and Q4 in C-S-H gel. Because only isolated SiO4 tetrahedrons (Q0 ) and Ca ions could be absorbed by the bone tissue, C3 S paste gradually transformed into a silica-rich gel. The fundamental reason for no decrease in volume of C3 S paste was that the SiO4 tetrahedron network still maintained the frame structure of C3 S paste during the implantation.