Objective: The aim of this study was to determine the effect of acidic solution on degradation of ionomeric and resin restorative materials through surface hardness, roughness and fluoride release measurements. Methods: Eighteen specimens of Fluroshield, Vitremer, and Ketac Molar, were prepared, following the manufacturer's instructions. The specimens were stored for 24h at 37°C and 100% humidity. After, they were polished, and submitted to the initial evaluation of surface hardness (3 indentations, 50 g for 10 s – Shimadzu HMV 2) and roughness (3 measurements per specimen, Ra – Surfcorder SE 1700). The specimens were randomly assigned into 3 groups, according to the immersion solution (n=6): 0.3% citric acid (CA), demineralization solution (DE), and remineralization solution (RE – artificial saliva/control). The specimens were individually immersed in 3 ml of the solutions, which were daily changed. After 15 days, surface hardness and roughness of the specimens were evaluated. Fluoride release was determined in the solutions within 15 days. Data were submitted to ANOVA and Tukey's test (α=0.05). Results: There was a significant reduction on hardness (KHN) of all materials, regardless the immersion solution (Fluroshield - before:25.8/ after:3.6; Vitremer - before:34.6/ after:5.8; Ketac Molar - before:38.6/ after:6.7). The immersion in CA significantly increased the roughness (μm) of Vitremer (before:0.5 /after:1.2) and Ketac Molar (before:0.7 /after:3). These materials showed the highest fluoride release (ppmF) in CA solution (Vitremer:39.6; Ketac:41.5). There was no significant difference on roughness of Fluroshield, regardless the immersion solution, however the fluoride release in DE(3.2) was significantly higher than in CA(1.9). Conclusion: Ionomeric materials were more susceptible to degradation in citric acid solution; however, they showed more fluoride release when submitted to acidic challenge.

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