Novel resin modified glass-ionomer cements with improved flexural strength and ease of handling

Poly(acrylic acid-co-itaconic acid) copolymers containing pendent methacrylates were synthesized and used to formulate redox-initiated in situ cured glass-ionomer cements (GICs) by mixing with reactive glass fillers (Fuji II LC). Various formulations for the redox initiator were studied, and flexural strength (FS) was used as a screening tool for optimization. Effects of molecular weight (MW), grafting ratio, comonomer, polymer content in the liquid composition, powder/liquid (P/L) ratio, and aging on FS were investigated. The results show that the in situ cured GICs demonstrated higher FS (89.6–123.2 MPa), as compared to commercial Fuji II LC GIC (57.1 MPa). The optimal concentrations for redox initiators were found to be 0.15% (by weight) for K2S2O8 and 0.2% for ascorbic acid (or 0.6% for microencapsulated ascorbic acid), respectively. Effects of MW, grafting ratio, P/L ratio and polymer content in the liquid formulation were significant. During aging, the cement showed an increase in strength over 24 h and then no change for time periods up to six months. SEM analysis supports the strength data associated with the formulations. The exotherm and setting time suggest that novel redox-initiated resin-modified GICs hold promise as biocompatible and workable cement for orthopedic applications.