Method: : Ten human maxillary central incisors were sectioned transversely at the cementoenamel junctions, and the crowns were discarded. The roots were embedded in blocks of high-speed polymerized acrylic resin and cut transversely into 1-mm sections. The second section of the cervical third of the root of each tooth was sectioned and divided into four parts. Each quarter was destined to the confection of the specimen and it was used four specimen to each root, one for each solution (n=10): G1- 15% EDTA; G2- 10% citric acid; G3- 0.2% chitosan and G4- control (distilled water). The specimen has received 50 µL of the solution for 5 minutes, and then, they were washed by deionized water. It was used a microhardness (Knoop hardness) with a load of 10g during 15 seconds.
Result: The results showed that 0,2% chitosan (24.5±6.5), 15% EDTA (24.4±7.0), and 10% of citric acid were capable to reduce the microhardness of the root dentin in a similar way among them, and statistically differ from the control group (36.9±7.9) (p<0,01).
Conclusion: Therefore, it was concluded that all solutions are able to reduce the dentin microhardness, and the control group did not modify the microhardness.