[Formation, composition, clinical implications and methods for removing the smeared layer from root canal walls].

A layer, which is readily detectable at higher magnifications with scanning electron microscope (sem) is consistently seen on canal walls that have been endodontically instrumented. This layer in the international bibliography reported as smeared layer. The surface of this layer is amorphous, irregular and granular. Although the composition of this layer has not been completely determined, it probably contains fine inorganic particles of dentin produced by mechanical preparation of root canal walls. As well as some organic material from necrotic or vital pulp tissue, bacteria and blood cells. The clinical importance of the smeared layer is still not fully understood. It may be beneficial since it is known to plug the orifices of the dentinal tubules and to reduce the permeability of dentin. In addition, the Smeared layer covering prepared areas of root canal prevents medicaments and filling materials from penetrating the dentinal tubules on even contacting the canal wall. The formation of this layer, the composition, the clinical importance and various methods for removing the smeared layer from the system of root canals, is the object of this paper.