Effects of NaHCO₃ on Properties of Sol-gel Calcium Silicate Cement

Objectives: Porous calcium silicate cement (CSC) synthesized via sol-gel process has been introduced in medical applications. However, the insufficient material strength and longer setting time are the major disadvantages of CSC. Sodium bicarbonate was reported as a catalyst for cement hydration. The purpose of this study is to investigate the effects of the additive of NaHCO₃ on the physicochemical properties of CSC. Methods: Sol-gel CSC powder were produced and mixed with 0%, 0.1%, 1%, 5% NaHCO₃ powder in weight respectively. The NaHCO₃ contained sol-gel CSC powder was mixed with distilled water at the powder to liquid ratio of 2.5 (g/ml) and the specimens were prepared for setting test, microhardness test and compressive strength test. Results: We found the setting time of sol-gel CSC declined when the content of NaHCO₃ increased. The sol-gel CSC contained 5% NaHCO₃ demonstrated the shortest setting time(22±3 min). In addition, the sol-gel CSC with more than 1% NaHCO₃ ingredient presented higher surface microhardness and compressive strength, if compared to those with 0.1% NaHCO₃ contained or without NaHCO₃. Conclusions: By adding 1% or 5% NaHCO₃, the setting reaction of sol-gel CSC would be enhanced, and the surface microhardness and compressive strength would be improved.