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Effect of the smear layer in the removal of calcium hydroxide from root canal walls

Background: The aim of this study was to investigate whether the smear layer influences the removal of calcium hydroxide from the root canal with manual or rotary instruments. Materials and Methods: The root canals of 48 freshly extracted single-rooted maxillary incisors were prepared to apical size 40 (n=40) and finally irrigated with sodium hypochlorite (group A), or ethylene diamine tetra acetic acid (EDTA) followed by sodium hypo chlorite (group B). 20 teeth were assigned to each group, while the remaining eight teeth served as positive and negative controls. Each group was divided into two subgroups of 10 teeth (subgroup I - calcium hydroxide was removed with master apical file; subgroup II - with profile file); and, in all removal procedures, citric acid was used for irrigation. The percentage of calcium hydroxide- [Ca(OH)2] coated surface area was calculated by image processing analysis. Results: Considering the root canal as a whole, the removal of Ca(OH)2 from the dentinal walls in group B showed significantly better results (P<0.05) as compared to group A. Conclusions: Under the conditions of this study, it can be concluded that the smear layer is important in the removal of calcium hydroxide.