The properties of experimental resin-modified glass-ionomer luting cements (RMGICs) containing novel monomers

To investigate working and setting times, compressive fracture strength (CFS), compressive modulus (CM), three-point flexure strength (TFS) and tensile flexure modulus (TFM) of commercial, control and experimental RMGICs.

RelyX Luting (RX, 3M-ESPE) and Fuji Plus (FP, GC), two control home liquids and eight new liquid compositions (F1-F4 and R1-R4) comprising different percentages of the monomer HPM (hydroxypropyl-methacrylate) and/or THFM (tetrahydrofurfuryl-methacrylate) with the original monomer HEMA (2-hydroxyethyl-methacrylate) were used in this study. The polymerization was initiated chemically (using benzene sulfonic acid sodium-salt in FP powder and potassium persulfate/ascorbic acid in RX powder). Home and experimental liquids were mixed with the corresponding commercial powder. An oscillating rheometer was used to measure the working and setting times (n=6). 20 cylinders per material (6.0±0.1mm height, 4.0±0.1mm diameter) were fabricated for CFS and CM testing, 20bars per material (25.0±0.1mm length, 2.0±0.1mm width, 2.0±0.1mm thickness) were made for TFS and TFM testing.

All RX compositions showed longer setting times (p≤0.0001) and lower CFS values compared to their FP counterparts (p≤0.0001). The TFS testing showed that commercial and home RMGICs behaved as brittle materials with linear load/deflection curve while experimental materials showed plastic ductile deformation before fracture. F3, F4 and F2 showed significantly higher CFS values compared to the corresponding home material (p≤0.0001).

All new experimental compositions demonstrated working and setting times that are clinically acceptable. The new experimental FP compositions containing THFM (especially F3 and F4) demonstrated improved mechanical properties compared to their corresponding home material.