Optimization of 3-butenoic acid-modified polyalkenoic acid for enhanced glass ionomer cement performance.

Objective: Glass ionomer cements (GICs) suffer from mechanical limitations due to rigid intermolecular hydrogen bonding in polyalkenoic acid (PCA) that impedes ionic cross-linking during setting. This study examined how molecular weight and solution concentration of modified polyalkenoic acid (PCA) containing 3-butenoic acid (VA) spacers at 8 mol% concentration (PCA-VA-8) influence comprehensive GIC performance.

Methods: PCA-VA-8 polymers with varying molecular weights (5.49 × 10 to 15.57 × 10) were synthesized via free radical copolymerization of acrylic acid, itaconic acid, and 3-butenoic acid by controlling initiator dosage. Experimental GICs were prepared using different PCA-VA-8 concentrations (40-60 wt%) and powder-to-liquid ratios (3.2:1 to 4.0:1). Mechanical properties were evaluated according to ISO 9917-1:2007 standards, while water sorption, solubility, aging resistance, and fluoride release were assessed over 4-week immersion periods.

Results: The optimal formulation (molecular weight ≈8 × 10, 50 wt% concentration, 3.6:1 powder-to-liquid ratio) achieved enhanced mechanical properties: flexural strength 54.14 ± 5.29 MPa, flexural modulus 19.00 ± 1.06 GPa, and compressive strength 221.35 ± 17.06 MPa (p < 0.05). This formulation showed 33 %-63 % higher flexural strength than commercial Fuji IX-GIC throughout 4-week water aging while maintaining excellent dimensional stability. Water sorption was reduced by 18 %-22 % during initial weeks compared to commercial materials, with solubility remaining comparable to controls (p > 0.05). Fluoride release analysis revealed an initial burst release of 4.1 μg/mL on day 1, followed by stabilization at 0.6-0.9 μg/mL from day 4 onward. Although lower than the initial release of commercial Fuji IX-GIC (6.2 μg/mL), the sustained fluoride levels remained above the therapeutic threshold necessary for remineralization and caries prevention.

Significance: VA-modified PCA enhances GIC mechanical properties through improved polymer chain flexibility while maintaining clinical requirements for water resistance and fluoride release, representing a promising advancement for next-generation restorative applications.