Abstract
Background and aims. The aim of the present study was to compare 1.3% sodium hypochlorite (NaOCl) in MTAD
(mixture of tetracycline isomer, acid, and detergent) for the removal of the smear layer and induction of canal erosion.
Materials and methods. 38 maxillary incisors were divided in three experimental groups of 10 and two positive and
negative control groups of each 4 teeth, and prepared using rotary files. In test groups, 1.3% NaOCl was used for 5, 10 and
20 minutes during preparation followed by MTAD as the final rinse. In negative control group, 5.25% NaOCl was used for
10 minutes followed by 17% Ethylenediamine Tetra-Acetic Acid (EDTA) as the final rinse. In positive control group, distilled
water was used for 10 minutes during preparation and then as the final rinse. The samples were examined under scanning
electron microscope, and the smear layer and dentinal erosion scores were recorded.
Results. Five and 10 min groups had significant differences with 20 min group (p < 0.05). In apical third, 5 and 10 min
groups had also significant differences with 20 min (p < 0.05). In the coronal thirds, when the time of irrigation with 1.3%
NaOCl increased from 5 min to 20 min, erosion also increased significantly. However, 5 and 10 min groups had no significant
differences with negative control group.
Conclusion. The use of 1.3% sodium hypochlorite for 5 and 10 minutes in the MTAD protocol removes the smear layer
in the coronal and middle thirds but does not induce erosion.