Effect of the smear layer on salivary bacterial leakage in endodontically treated teeth

The success of endodontic treatment depends on the method and quality of cleaning, disinfection and three-dimensional sealing of the root canal. The smear layer can play an important role in the success or failure of endodontic treatment. There is controversy over the presence or removal of the smear layer in relation to the success or failure of endodontic treatment. This study used standard methods of endodontic treatment and whole human saliva to evaluate the effect of the smear layer on salivary bacterial leakage in endodontically treated teeth.

In this in vitro study, 48 human single- and multiple-rooted teeth were randomly divided into two experimental groups of 20 and two negative and positive control groups of 4 teeth. After access cavity preparation the root canals were prepared with crown-down technique and irrigated with 10 mL of 5.25% sodium hypochlorite solution. The canals in one group were irrigated with 17% EDTA and 5.25% sodium hypochlorite to remove the smear layer and in the other only with 5.25% sodium hypochlorite to leave the smear layer in place. Then the teeth were sterilized by autoclave and obturated with gutta-percha sterilized with ethylene oxide and Tubliseal sealer under aseptic conditions. Two mL of human saliva were collected from two persons and injected into the coronal portion of the samples, which was repeated for four months. Leakage of the samples was examined twice daily. Data was analyzed with chi-squared test at a confidence interval of 95%.

Presence or absence of the smear layer had no significant effect on salivary bacterial leakage of different root canals filled with gutta-percha and Tubliseal sealer (p value = 0.515), although the number of cases with contamination and leakage of saliva in the group with the smear layer (55%) was more than that in the group without the smear layer (44%).

The results showed no significant effect of the smear layer on coronal leakage of human saliva into obturated canals.