RESUMO
BACKGROUND/PURPOSE: Strontium ion may play a role similar to calcium ion in enamel remineralization. The aim of this study was to investigate the effect of strontium ion concentration gradient on the demineralization of enamel. METHODS: Citric acid and sodium citrate were used to prepare 16 different experimental acidic solutions with four different pH values (2.5, 3.5, 4.5, and 5.5) and four different strontium ion concentrations (0 M, 10-4 M, 10-3 M, and 10-2 M). Forty-eight human enamel samples were divided into 16 groups (n = 3) and immersed into the 16 different acidic solutions for 3 min. The phosphorus ion concentrations in 16 different acidic solutions were measured and compared. The enamel surface hardness was measured with a Vickers hardness tester. The energy dispersive spectrometer was used to detect the strontium ion content in the enamel surface. RESULTS: Addition the strontium ions to the acidic solution could reduce the dissolution of the enamel. At pH 3.5 and pH 5.5, significantly lower phosphorus ion concentrations were detected in the acidic solutions with the addition of 10-2 M strontium ions. There was a less reduction of enamel surface hardness, while the strontium ion concentration increased in the acidic solution. At pH 2.5, the addition of 10-4 M, 10-3 M, or 10-2 M strontium ions to the acidic solution resulted in a significant increase in the strontium ion content in the enamel surface. CONCLUSION: Strontium ion can decrease the dissolution of the enamel and prevent the enamel surface hardness loss in acidic environment.