The use of bioactive microspheres as bone filling materials has received much attention due to their ability to fill the bone defects with irregular and complex shapes and sizes. Divalent Mg(2+) modified silicate-based diopside (DIOP: CaMgSi(2)O(6)) and tetravalent Zr(4+) modified silicate-based baghdadite (BAGD: Ca(3)ZrSi(2)O(9)) ceramics have shown excellent in vitro bioactivity for potential bone repair application. However, their in vivo osteogenesis has not been systematically investigated. The aim of this study is to prepare DIOP and BAGD ceramic microspheres and investigate their in vivo osteogenesis. DIOP and BAGD ceramic spheres with loose microstructure were successfully prepared. The dissolution ability of two silicate-based bioceramics was investigated by testing the release of SiO 44- ions after soaking them in phosphate buffered saline. The ceramic spheres were implanted into supracondylar site of the femur defects in Wistar rats and the degree of in vivo osteogenesis was evaluated by hematoxylin and eosin (H and E), Safranin O staining, tartrate-resistant acid phosphatase (TRAP) staining, and immunohistochemistry (type I collagen: Col I, osteopontin: OPN) analyses. The results have shown that BAGD spheres induced a higher rate of new bone formation in the defects than did DIOP and β-tricalcium phosphate (β-TCP) spheres. Immunohistochemical analysis showed greater expression of Col I and OPN in BAGD group compared to DIOP and β-TCP groups. The study indicates different ion modification playing an important role to regulate the in vivo osteogenesis of silicate-based bioceramics. BAGD spheres are a promising bone filler material due to their significantly enhanced osteogenesis, compared to β-TCP spheres.
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