Microhardness of different esthetic restorative materials: Evaluation and comparison after exposure to acidic drink

Background: Acidic beverages, such as soft drinks (orange juice and cola), can produce erosion of resin composites. The aim of this in vitro study was to evaluate the effect of immersion in acidic drink on the Vickers microhardness (VK) of different esthetic restorative materials (one nanohybrid Ormocer‑based composite, one nanoceramic composite, one nanofilled composite, and one microfilled hybrid composite). Materials and Methods: In this in vitro study, thirty specimens of each esthetic restorative material were divided into three subgroups (n = 10): specimens of group 1 were used as control, specimens of group 2 were immersed in 50 ml of acidic drink for 1 day, specimens of group 3 were immersed in 50 ml of acidic drink for 7 days. Data were analyzed by Shapiro–Wilk test to assess the normality of the distributions followed by nonparametric Kruskal–Wallis analysis of variance and Mann–Whitney U‑test comparison test among groups. A significant level of α = 0.05 was set for comparison between the groups. Results: Mann–Whitney U‑test showed that each material showed lower microhardness values after immersion in acidic solution (P < 0.05). Paired t‑test confirmed that microhardness for each composite did not change after immersion in distilled water (Control group) (P > 0.05). Significant changes were registered for all restorative materials after immersion in acidic solution for 1 day and 7 days (P < 0.05). Conclusion: The Filtek Supreme XTE, a nanofilled composite, and Admira Fusion, a nanohybrid ormocer‑based composite, showed the best behavior. The Ceram X Universal (nanoceramic composite) although reached lower hardness values than the previous materials, but resisted well to the 1 week immersion in soft‑drink. Finally, the Gradia Direct achieved the most disappointing results: Low microhardness values are justified by the nature of its filling (microfilled hybrid composite).