Belizario LG, et al. - Here, the physicians assessed dentin surface cleanliness based on the presence of a smear layer and the number of open dentin tubules. In addition, they examine the chemical composition of residues after canal irrigation with a 1% peracetic acid solution (PA) at a low or high concentration of hydrogen peroxide during the preparation of intracanal fiber posts. When compared with PA 1% with a high concentration of hydrogen peroxide, PA 1% with a low concentration of hydrogen peroxide yielded a lower amount of smear layer and a larger number of open dentin tubules in the dentin of the post space, despite maintaining a similar oxygen concentration in these dentin residues.