Time-dependent Variation in Compressive Strengths of Three Posterior Esthetic Restorative Materials: An in vitro Study

Abstract

Aim: To compare the compressive strengths of composite resins and resin-modified glass ionomer cements (RMGICs) at different times. Materials and methods: A total of 36 samples were prepared, 12 samples of each group, composite resins Filtek Z 250, Filtek Z 350, and resin-modified glass ionomer cement. Compressive strengths of specimens were measured after 1, 24 hours, and 7 days. Test was carried out on a "Universal Testing Machine" with cross-head speed of 5 mm/min. Results: There was a significant difference between all the three restorative materials. Analysis of variance showed that mean compressive strengths of Z 250 after 1, 24 hours were higher than Z 350 and RMGIC (p < 0.05). The mean compres-sive strengths were reduced after 7 days in all the three groups, but after 7 days, the values of Z 250 when compared with the Z 350 and RMGIC were higher. Conclusion: The study demonstrated that compressive strengths of hybrid composite resins (Z 250) were significantly higher than that of nanocomposites (Z 350) and RMGIC.