SMEAR LAYER AND ITS CONSEQUENCES IN DENTISTRY

When tooth is cut instead of being uniformly sheared, the mineralized matrix shatters. Considerable quantities of cutting debris, made up of very small particles of mineralized collagen matrix are produced. Existing at the strategic interface of restorative materials and the dentin matrix, most of the debris are scattered over the enamel and dentin surfaces to form what is known as the smear layer.As it is a very thin layer and is soluble in acids, the smear layer will not be apparent on routinely processed specimens examined with the light microscope. This may be the reason why smear layer received little attention by restorative dentists. When examined under the scanning electron microscope, the smear layer will rarely be discernible on specimens of mineralized teeth because it will be dissolved during the process of demineralization. Demineralized specimens appear on electron microscopic examination as a uniform sludge, relatively smooth and featureless.