Comparative Evaluation of Two Modified Glass Ionomer Cements with Conventional Glass Ionomer Cement for Fracture Toughness using 3-point Bending Test.

OBJECTIVE: The purpose of this study was to evaluate and compare the fracture toughness of Advanced glass hybrid Glass Ionomer Cement (GIC), Zirconium reinforced GIC and conventional GIC using 3-point bending test. MATERIALS AND METHODS: Three groups were formed in the present study, Group 1 (Hybrid GIC), Group 2 (Zirconomer Improved), Group 3 (Conventional GIC) which were tested at 24 hours and 7 days time interval according to their storage time in artificial saliva. Samples of each material were prepared with the help of customized mould of dimensions 25 mm*5 mm*2.5 mm and stored for 24 hours and 7 days in artificial saliva. The fracture toughness testing was done in a 3-point bend apparatus using Universal Testing Machine with a crosshead speed of 1 mm/min until failure. The mean fracture toughness values were compared using two-way ANOVA followed by post hoc (Bonferreni). The values at 24 hours and 7 days were compared using paired t-test. RESULTS: At 24 hours and 7 days, Advanced Glass Hybrid GIC showed the highest fracture toughness values, while the lowest values were observed with conventional GIC. A statistically significant difference was seen between Advanced Glass Hybrid GIC and conventional GIC at 24 hours. Zirconium reinforced GIC showed intermediate values. In intra-group comparison, an increase in values was seen with all 3 materials at 7 days, however the difference was statistically insignificant. CONCLUSIONS: Advanced Glass Hybrid and Zirconium reinforced GIC showed better fracture toughness than the Conventional GIC. Fracture toughness of GICs was influenced by time.