[Should the dentin smear layer be preserved or eliminated? (Review of the literature)].

The smear layer is a direct consequence of instrumentation of the root canal wall. Hand instrumentation as well as ultrasonic instrumentation produce a smear layer on the canal wall. This smear layer is composed of dentine, remnants of pulp tissue and odontoblastic processes and bacteria in an infected canal. Removal of the smear layer is accomplished by the irrigation of root canals with EDTA (17%) followed by NaOCl (5.25%). Permeability of the dentine is increased by the removal of smear layer. In this way the bacteria within the infected tubuli can be more easily destroyed by an intracanal dressing. Whether the removal of smear layer decreases the apical leakage is uncertain. To establish the clinical consequences from removal or preservation of the smear layer, further research is needed.