Real-time atomic force microscopy of root dentine during demineralization when subjected to chelating agents

To explore the potential of atomic force microscopy (AFM) for the examination of changes to dentine surfaces during demineralization and evaluate qualitatively the effect of EDTA, EDTAC and citric acid.

Nine canine teeth were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, each root was embedded in an epoxy cylinder and discs approximately 5 mm thick were cut. A standard metallographic procedure was then used to prepare the surfaces for observation. From the central portion of these samples, two specimens were symmetrically prepared per tooth so that a total number of 18 samples was produced. To allow the use of a liquid cell during AFM, the samples were embedded in silicone rubber and were then randomly divided into three groups, as follows: group 1: 17% EDTA (pH 7.7), group 2: 17% EDTAC (pH 7.7) and group 3: 10% citric acid (pH 1.4). Topographical images were acquired during the demineralization process, allowing real-time observation of the dentine surface. Two operators assigned scores to the AFM images using a double-blind method. anova analysis with random effects (P < 0.05) was used to compare the results.

The average scores were 6.13 +/- 0.35 for EDTAC, 7.36 +/- 0.23 for EDTA and 14.55 +/- 1.21 for citric acid. Citric acid was statistically different from EDTA and EDTAC while EDTA and EDTAC were not statistically different.

The most effective demineralizing substance was citric acid. The methodology developed for real-time observation of dentine surfaces is a valuable method to evaluate demineralization.