A smear layer is created by the action of metallic instruments on dentine, especially rotary instruments. It is composed of dentine filings, pulpal tissue remnants and may also contain microbial elements. It may occlude dentine tubules thus harbouring bacteria, and may contain a bacterial plaque on the canal walls. It has been shown that gutta-percha penetrates the dentine tubules when the smear layer has been removed.
It is therefore suggested that the root canal should be irrigated with an EDTA solution to remove the smear layer, followed by a final irrigation with sodium hypochlorite, prior to drying and obturating the canal.
It is therefore suggested that the root canal should be irrigated with an EDTA solution to remove the smear layer, followed by a final irrigation with sodium hypochlorite, prior to drying and obturating the canal.