Strong effect on dentin after the use of high concentrations of citric acid: An assessment with co-site optical microscopy and ESEM

Objectives To perform a longitudinal analysis of the effect of four substances (citric acid at 1%, 5% and 10% concentrations and 17% EDTA) on dentin. Methods Sixteen human molars had their crowns removed exposing cervical root dentin. A grinding procedure was used to produce a standardized smear layer and to create a smooth surface for analysis. Environmental scanning electron microscopy (ESEM) was used for qualitative observations while co-site optical microscopy (CSOM) and image analysis (IA) provided a quantitative comparison of the effect of the substances for several experimental times from 15 to 300 s. The methods allowed the observation of the same areas after each experimental time. The open tubule area fraction was measured for several CSOM image fields, at each experimental time, for the four substances. Thus, it was possible to follow the phenomenon and quantitatively analyze the effect of the substances. Kolmogorov–Smirnov, Kruskal–Wallis H and Wilcoxon signed-ranks (with Bonferroni correction) tests were used to analyze the data. The level of significance was set at p < 0.05. Results The CA solutions showed the greatest chelating effect, which was proportional to concentration (EDTA: 9.4–32.8% (15–300 s); 1% CA: 21.1–32.2% (15–300 s); 5% CA: 32.4–43.1% (15–300 s); 10% CA: 35.1–39.5% (15–30 s). Erosive effects were observed on inter and peritubular dentin for 5% CA and 10% CA after 60 s. Significance ESEM allowed a detailed qualitative comparison of the effect of the four substances. CSOM and IA provided a quantitative comparison method with good statistical significance. Future studies should focus on the consequences of dentin erosion caused by citric acid.