Comparison of Mechanical Properties of Resin Composites with Resin Modified Glass Ionomers

Statement of Problem: There are controversial reports regarding physical and mechanical properties of resin composites and glass ionomer cements. Some revealed higher strength and hardness for resin composites while others showed a comparable value for glass ionomer cements. Evaluation of mechanical properties of different types of resin composites in comparison with resin modified glass ionomers is not widely studied. To measure and compare the flexural strength and Vickers hardness of three resin composites and two resins modified glass ionomer cements before and after ageing. Three resin composites, i.e. Filtek Supreme XTE (3M ESPE), Ice (SDI), Gradia (GC), and two resins modified glass ionomers, i.e. Fuji II LC (GC) and Riva Light Cure (SDI), were selected. Ten bar-shaped specimens were prepared for each material and cured using LED curing light. After 24 hours storage in distilled water at 37oC, the specimens were randomly divided into two equal groups (n=5). The first group was tested as a baseline and the second group was restored at 37oC for another 29 days. Flexural strength was performed by four-point bending test using universal testing machine at crosshead speed of 0.5mm/min, and the maximum load at failure was recorded. The specimen’s halves were used for evaluating Vickers hardness, using a Digital Hardness Tester (300 g/15 sec) and the Vickers hardness number (VHN) was recorded. Data were analyzed using one-way analysis of variance (ANOVA), Tukey’s and student’s t-test. After 24 hours of immersion, the highest hardness number was found for Filtek Supreme and Ice and the highest flexural strength was obtained for Gradia. After 30 days of storage, hardness of Fuji II LC and Gradia showed a significant decrease; flexural strength of Ice and Fuji II LC revealed a significant increase while Gradia and Filtek Supreme showed a significant decrease. Resin modified glass ionomers showed a comparable result for hardness and flexural strength with some of the tested resin composites and lower values than some others.