Time-Dependent Effect of Various Irrigants for Root Canal on Smear Layer Removal

Existence of smear layer in root canals caused by instrumentation is believed to prevent penetration of irrigating agents, thereby resulting in endodontic treatment.

To compare and evaluate the effectiveness of two irrigants: 17% ethylenediaminetetraacetic acid (EDTA) and mixture of tetracycline isomer, an acid, and a detergent (MTAD) as final agents for eliminating the smear layer.

We included 50 human lower premolar teeth whose crowns were sectioned at cementoenamel junction. The sample was randomly grouped into five groups, each with 10 teeth. Group 1: 1 mL of 17% EDTA as final rinse for 1 min, Group 2: 1 mL of 17% EDTA for 30 s, Group 3: 5 mL of MTAD for 2.5 min, Group 4: 5 mL of MTAD for 5 min, and Group 5: saline. The specimens were sectioned vertically all along the long axis and fixed on an aluminum stub for gold ion sputtering. Scanning electron microscope was used to observe the specimens, and photomicrographs were taken at coronal, middle, and apical thirds of canal, and assessed by Torabinejad scoring system by two examiners, and the observations were analyzed statistically.

When Group 1 and Group 2 and Groups 3 and 4 were compared, we found a significant variation in removal of smear layer at cervical and middle thirds, and insignificant difference at apical third. In comparison with EDTA and saline, MTAD was more efficient significantly in middle and cervical thirds and insignificant at apical third.

MTAD is an efficient irrigant for removing smear layer than EDTA and saline.