2014 Volume 57 Issue 6 Pages 492-501
Purpose: Bioactive glasses (BAG) raise the activity of osteoblasts in vitro, but it remains unclear whether they enhance the bone formation activity or not in defects of rat parietal bones which have poor bone marrow. Strontium (Sr) enhances the differentiation of preosteoblast to osteoblast and activates it, and also inhibits the differentiation of osteoclast and its activity, thus promoting bone formation. Therefore we created BAGs which contain Sr to enhance the osteogenic property of BAGs and tested their biocompatibility, bioactivity and promotion of bone formation in vivo.
Materials and Methods: BAG (Sr0) containing 53 SiO2-20 CaO-23 Na2O-4 P2O5 (wt%) and BAG (Sr20) containing 53 SiO2-16 CaO-4 SrO-23 Na2O-4 P2O5 (wt%) were prepared using the melt-quench method. Some discs (1 mm thickness, 10 mm diameter) and powders (particle size 250-300 μm) were made. Discs of Sr0, Sr20 and hydroxyapatite were implanted subcutaneously in rats. One month after the operation, the animals were sacrificed and histological observations were performed. Calvarial defects of 8 mm diameter were made surgically in the rats. Powder of Sr0 or Sr20 was implanted into the defects. The rats were divided into three groups: Control: blood clot only, Sr0: defects were filled with Sr0 powder; Sr20: defects were filled with Sr20 powder. At 1, 3 and 6 months after the operation, rats were sacrificed and analyzed by optical microscopy. Formation of new bone and solubility of BAGs were evaluated histomorphometrically.
Results: The histopathological reactions of Sr0 and Sr20 showed good biocompatibility similar to that of hydroxyapatite. No new bone formation was noted at the center of the calvarial defects of the Control group. At 6 months, Sr0 particles were surrounded by fibrous tissue, and new bone formation was not observed around the particles. Sr20 particles had dissolved markedly, and their cross-sectional area had decreased significantly in comparison to Sr0. At 6 months, new bone formation in the bone defects had increased in comparison to Sr0. It is suggested that Sr ions released from Sr20 promote new bone formation.
Conclusion: The present study suggested that Sr-substituted BAG should have good biocompatibility and enhance osteogenic property.
