Effects of added sodium alginate on mechanical strength of apatite cement

Effects of added sodium alginate on the mechanical strength of Biopex®, one type of apatite cement, were investigated since sodium alginate addition is very effective for Biopex® to acquire anti-washout property. Addition of sodium alginate into the liquid phase of Biopex® resulted in a slower transformation to apatitic monolith. As a result, mechanical strength of set Biopex® in terms of diametral tensile strength (DTS) decreased when it was hardened in an incubator kept at 37°C and 100% relative humidity for 7 days. However, DTS value increased with increase in the amount of added sodium alginate when the Biopex® paste was immersed in 0.9% saline at 37°C for 7 days. Set Biopex® with less sodium alginate also showed larger porosity. Based on these findings, we concluded that added sodium alginate was effective in increasing the mechanical strength of Biopex® by inhibiting liquid penetration into its paste when it is exposed to body fluids.