Self-setting β-tricalcium phosphate granular cement at physiological body condition: effect of citric acid concentration as an inhibitor

The aim of this study is to investigate the effect of citric acid (CA) concentration as an inhibitor on the properties of β-tricalcium phosphate (β-TCP) granular cement. In this study, β-TCP granules were exposed to an acidic calcium phosphate solution containing 0.01 mol/L, 0.10 mol/L, and 1.00 mol/L of CA at physiological body conditions for 10 min. These specimens were denoted as 0.01 mol/L CA, 0.10 mol/L CA, and 1.00 mol/L CA, and its properties were characterized throughout the study. Physical appearance results showed that increasing citric acid concentration in an acidic calcium phosphate solution up to 1.00 mol/L reduced the self-setting ability of β-TCP granules. Meanwhile, compositional and morphological analyses showed the amount of dicalcium phosphate dihydrate (DCPD) crystals that precipitated and interlocked between β-TCP granules decreased when the concentration of citric acid increased. The decreasing trend of DCPD formation in set specimens increased its porosity and reduced the compression strength up to 27.4%. Therefore, these findings evinced that by altering the concentration of citric acid in an acidic calcium phosphate solution, the setting reaction of β-TCP granules at physiological body condition was inhibited.