Synergistic effect of ion release and micromorphology on biomineralization, cytocompatibility and osteogenesis of Li+/Na+ exchanged LD glass-ceramic in vitro.

Lithium disilicate (LD) glass-ceramics have adequate mechanical properties and are considered as a candidate for repairing large bone defects. However, LD glass-ceramic is an inherently inert restorative material, which cannot induce new bone tissue. In the present study, LD glass-ceramics were ion-exchanged at 235 °C for 16 h, 64 h and 128 h in a mixed salt bath of sodium nitrate and potassium nitrate (1:1 M ratio) respectively. A gradient concentration distribution of Na+-rich layer was obtained by Li+/Na+ exchange and Na+ ions were released from the Li+/Na+ exchanged LD glass-ceramics in an aqueous condition. The hydroxyapatite (HA) layer was formed on Li+/Na+ exchanged LD glass-ceramic and exhibited a significant exchange time-dependent after soaking in the simulated body fluid (SBF). Moreover, the Li+/Na+ exchange treatment could improve cell adhesion, proliferation and osteogenic differentiation of LD glass-ceramic significantly, and long-time treatment could achieve a better performance. Therefore, ion-exchange process is a feasible strategy to promote the surface biomineralization, cytocompatibility and osteogenesis of LD glass-ceramics. These results suggest that Li+/Na+ exchange is a promising process for LD glass-ceramic application in clinical orthopedic reconstruction. [ABSTRACT FROM AUTHOR]