A layer, which is readily detectable at higher magnifications with the Scanning Electron Microscope (SEM} is consistently seen on canal walls that have been endodontically instrumented. This layer covers and obscures the underlying canal wall and is commonly referred to as the "Smeared Layer". Although this layer is not in its specific form, but it has distinctive features that can differ from another layer. The clinical implications of the smear layer are 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 has been shown to be a protective diffusion barrier and capable of preventing bacterial penetration into dentinal tubules. On the other hand, the smeared layer may be deleterious as it is a layer of material which covers prepared areas andprevents medicaments and filling materials from penetrating the dentinal tubules or even contacting the canal wall. Lack of understanding of the smeared layer has prompted some investigators to suggest further research is needed. Whether this layer should be removed is still unknown and controversial. Each opinion has its own reasons. Based on the reference observation, the removal of smear layer exposed the dentinal tubules and creating a much more irregular surface. This irregular surface produced greater adhesion, especially when a good quality sealer was used.