The Investigation of Bioactivity and Mechanical Properties of Glass Ionomer Cements Prepared from Al2O3-SiO2 Glass and Poly(γ-glutamic acid)

The glass ionomer cement as one of the dental cements has been subjected to be widespread application in restoring tooth structure. Most of glass ionomer cements employ the poly(acrylic acid) (PAA) as the liquid phase, but the presence of PAA inhibits the apatite formation on the surface in the body environment, which is an essential requirement for exhibiting bone-bonding ability (bioactivity). In this study, poly(gamma-glutamic acid) (gamma-PGA), a kind of biopolymer, was utilized for cement preparation. The effort of preparation parameters including the glass powders/liquid ratio (P/L) and the concentration of gamma-PGA on diametral tensile strength were investigated. A maximum diametral tensile strength value of 11.88 +/- 1.43 MPa was obtained when the cement sample was prepared by P/L ratio of 1:1 and the gamma-PGA concentration of 30% after aging for 3 days. The TF-XRD patterns, SEM images, and EDX spectra suggested that the cement induced a precipitation of calcite on the surface after 7 days of immersion in stimulated body fluid (SBF), although the apatite formation was not observed. The present results suggest that the cement has potential to show bioactivity in vivo, because calcite is also reported to be bioactive.