Endodontic irrigating solutions may interact chemically with one another. This is important, because even when solutions are not admixed, they will come into contact with one another during an alternating irrigation technique, forming unwanted by-products, which may be toxic or irritant. Mixing or alternating irrigants can also reduce their ability to clean and disinfect the root canal system o...

The smear layer was first described by McComb in a scanning electron microscope (SEM) study. The smear layer consists of organic and inorganic substances, including fragments of odontoblastic processes, dentinal shaving, microorganisms, and necrotic materials. Presence of this smear layer prevents penetration of intracanal medication into the irregularities of the root canal system and the dent...