Synthesis and preparation of novel 4-arm star-shape poly(carboxylic acid)s for improved light-cured glass-ionomer cements

Objective: The objective of this study was to synthesize and characterize novel 4-arm star-shape poly(acrylic acid)s (poly(AA)s) via atom-transfer radical polymerization (ATRP) technique, tether in situ light-curable methacrylate functionalities onto the poly(AA) backbone, use these star-shape poly(AA)s to formulate the light-cured glass-ionomer cements (LCGICs), and evaluate the mechanical strengths of the formed cements. Materials and methods: The 4-arm poly(AA)s were synthesized using ATRP and tethered with either 2-isocyanatoethyl methacrylate (IEM) or glycidyl methacrylate (GM). The polymers were formulated with 2-hydroxyethyl methacrylte (HEMA) or methacryloyl beta-alanine (MBA), water, initiators, and Fuji II LC filler. Compressive strength (CS) was used as a tool to evaluate the formed cements. The specimens were conditioned in distilled water at 37 °C for 24 h prior to testing. Results: The 4-arm poly(AA) showed a lower viscosity as compared to its linear counterpart. Both IEM-tethered and GM-tethered 4-arm poly(AA) constructed LCGICs showed significantly high mechanical strengths. Both types of co-monomer and grafting agent dramatically affected the mechanical strengths. The MBA-containing poly(AA) cements exhibited much higher CS than the HEMA-containing cements. The IEM-tethered poly(AA) cements showed much higher CS and DTS than the GM-tethered cements. Conclusions: This study developed a novel light-curable 4-arm star-shape poly(AA) system. The system was 13% in CS, 178% in DTS and 123% in FS, compared to Fuji II LC.