Water-Uptake and Mechanical Properties of Experimental Resin-Modified Glass-Ionomer Cements (RMGICs).

Objectives: To investigate water-uptake, compressive fracture strength (CFS), compressive modulus (CM), three-point flexure strength (TFS) and flexural modulus (TFM) of four experimental RMGIC liquid compositions compared to two commercial and two in-house RMGICs based on the commercial materials used.
Methods: Two commercial RMGICs included in this study were Fuji Plus (GC, Japan) and RelyX Luting (3M ESPE, USA). Two additional in-house liquids were prepared based on the commercial materials published composition data. Four experimental liquid compositions (F1 and F2 based on Fuji Plus, R1 and R2 based on RelyX Luting) were prepared replacing either 50% of hydroxyethyl-methacrylate (HEMA) with tetrahydrofurfuryl-methacrylate (THFM) in F1 and R1 or 30% in F2 and R2 compared to the in-house liquids. Six discs for water-uptake (16mm-diameter, 1mm-thickness), twenty cylinders (6mm-height, 4mm-diameter) for CFS and CM and twenty bars (25mm-length, 2mm-width, 2mm-thickness) for TFS and TFM, respectively, were prepared at the manufacturers recommended powder:liquid mixing ratio. The powder used was the same corresponding commercial powder. Data were analysed using one-way ANOVA followed by post-hoc Tukey test at a significance level of p=0.05.
Results: All experimental compositions showed significantly lower weight change compared to the commercial materials (p<0.001). All experimental materials showed improved mechanical properties (CFS and TFS) compared to their in-house counterparts (p≤0.013), except CFS of R1 (p=0.734) and TFS of R2 (p=0.781). Two compositions (F1 and F2) showed significantly higher CFS compared to RelyX Luting and the two in-house materials (p<0.001). F1 moreover presented significantly higher CM (p≤0.04) and TFM (p<0.001) values compared to RelyX Luting and the two home materials.
Conclusions: Replacement of HEMA with THFM reduced the water-uptake, a common problem associated with RMGICs. Two experimental compositions (F1 and F2) showed improved mechanical properties compared to RelyX Luting but further modifications of the remaining experimental compositions is required to improve their strength.