Effect of duration of irrigation with NaOCl in clinical protocol of MTAD to removal of smear layer and creating dentinal erosion

Abstract

The aim of the present study was to compare the use of 1.3% sodium hypochlorite (NaOCl) for 5, 10 and 20 minutes in the MTAD (A mixture of tetracycline isomer, acid, and detergent) clinical protocol for the removal of the smear layer and induction of canal erosion. Materials and methods: 38 maxillary incisors were divided into three experimental groups of 10 and two positive and negative control groups of 4 and prepared using rotary files. In the test groups, 1.3% NaOCl was used for 5, 10 and 20 minutes during preparation followed by MTAD as the final rinse. In the negative control group, 5.25% NaOCl was used for 10 minutes followed by 17% Ethylenediamine Tetra-Acetic Acid (EDTA) as the final rinse. In the positive control group, distilled water was used for 10 minutes during preparation and then as the final rinse. The score of the smear layer and the extent of erosion of dentinal tubules were visualized under a scanning electron microscope. Results: For the score of smear layer, In the coronal thirds, no significant differences were observed between 5 and 10 min groups. However, both 5 and 10 min groups had significant differences with 20 min group (p <0.05). In apical third, there were no significant differences between 5 and 10 min groups and both groups had significant differences with 20 min (p<0.05). For the score of erosion, in the coronal thirds, when the time of irrigation with NaOCl 1.3% increased from 5 min to 20 min, erosion also significantly increased. However, both 5 and 10 min groups had no significant differences with negative control group. Conclusion: Use of 1.3% sodium hypochlorite for 5 and 10 minutes in the MTAD protocol, remove the smear layer in the coronal and middle thirds and do not induce any erosion.