The influence of the smear layer on dentinal tubule penetration depth by different root canal sealers - An in vitro SEM study

Objective: The aim of this in vitro study was to evaluate the influence of smear layer on the penetration depth of three different root canal sealers into the dentinal tubules. Study Design: Fifty two recently extracted human single-rooted teeth (> 20 mm long) were selected. After chemomechanical preparation using K-files and 1% sodium hypochlorite solution, the samples were randomly divided into two equal groups: group A: smear layer remained intact; group B: complete removal of smear layer using 15% aqueous EDTA. Two teeth from each group were used as controls. Eight teeth from each group were obturated with laterally condensed gutta-percha points and sealers Endoseal, Apexit, and AH-Plus, respectively. The penetration of sealers into the dentinal tubules was assessed using scanning electron microscope (SEM). Statistical analyses of the data were performed using one-way ANOVA test. Post-hoc comparisons by the Bonferroni test were used to determine whether the differences between the examined sealers were statistically significant. Results: Smear layer obstructed all the sealers from penetrating dentinal tubules. In contrast, smear layer removal allowed the penetration of all sealers to occur to a varying depth with Apexit and AH-Plus penetrating statistically significantly deeper than Endoseal. Conclusion: Smear layer plays an important role in sealer penetration into the dentinal tubules, as well as in the potential clinical implications.