Scanning Electron Microscopic Investigation of the Smeared Layer on Root Canal Walls

By Mader C, Baumgartner C, Peters D

Date: 01/1984
Journal: JOE


  • Purpose: investigate the morphological characteristics of the smeared layer
  • N= 5 extracted human mandibular molars with a single canal in the distal root.
  • Materials/Methods:

oDistal canals were instrumented by one operator using step back (K files) reaching size #50 under 3ml 5.25% NaOCl irrigation.

oRoots were longitudinally grooved, fractured in half with cutting pliers, and prepared for SEM evaluation

oThe smeared layer was examined from two different perspectives. First, to evaluate the superfacial layer and depth of the layer within the tubules.

Most highlighted Results:

  • The surface of the smeared layer was typically amorphous, irregular, and granular.
  • The smeared material should be thought of as thin layer on the surface of the canal wall and the smeared material which is packed into the dentinal tubules.
  • Uninstrumented areas displayed no smeared layer, however, occasional pieces of debris were seen.
  • The smeared layer was typically found to be about 1 – 2μm thickness and the depth up to 40 μm.

Clinical significance

  • Both the surface smeared layer and packed tubular material result directly from the instrumentation used to prepare the canal wall. Irrigation with NaOCI did not remove smear layer.