by Omid Mehdipour, DDS Donald J. Kleier, DMD Robert E. Averbach, DDS
Omid Mehdipour, DDS International Student Program Donald J. Kleier, DMD Professor and Chairman Robert E. Averbach, DDS Professor of Endodontics Division of Endodontics University of Colorado School of Dental Medicine Aurora, Colorado
Abstract Sodium hypochlorite (NaOCl) in various concentrations is the most widely used endodontic irrigant, but it can be an irritant to vital tissues. There are several reports about the complications of irrigation with NaOCl during root canal therapy. Most of the complications are the result of accidental extrusion of the solution from the apical foramen or accessory canals or perforations into the periapical area. This article is a review and comparison of all reported NaOCl accidents in the literature. The impetus behind root canal cleaning and shaping is the elimination of tissue remnants, bacteria, and toxins from the root canal system. This is generally accepted to be a major factor in the success of root canal treatment. Mechanical procedures alone are insufficient for total canal cleaning. Residual pulpal tissue, bacteria, and dentin debris may persist in the irregularities of canal systems. Therefore, irrigating solutions should support and complement endodontic preparation. These irrigants should flush out dentin debris, dissolve organic tissue, disinfect the canal system, and provide lubrication during instrumentation, without irritating the surrounding tissues. Some of the irrigants currently used include hydrogen peroxide, physiologic saline, water, sodium hypochlorite (NaOCl), chlorhexidine, and electrochemically activated water. Because of its physicochemical and antibacterial properties, NaOCl is one of the most popular irrigants. A 0.5% solution of NaOCl was used effectively during World War I to clean contaminated wounds.1 In 1920, Crane described the use of Dakin's solution (NaOCl buffered with sodium bicarbonate) for root canal debridement and sterilization. Since then NaOCl has become a popular and effective intracanal irrigant.2 It is an
inexpensive, readily available, and easily used chemical that usually rates well in research.3,4 A variety of NaOCl concentrations ranging from 0.5% to 5.25% have been advocated, as well as a variety of temperatures. The longer the solution can remain in contact with tissue, the higher the temperature of the solution, and the higher the concentration, the greater the ability of NaOCl to dissolve the tissue.5-7 The optimum concentration for use clinically is still a matter of controversy. Consequently, the clinician must decide on the concentration and temperature of the NaOCl and the potential consequences of this choice.5,8,9
Advantages of NaOCl
The ability of NaOCl to dissolve organic soft tissue of the pulp and predentin is a result of oxidation. The powerful oxidative activity of hypochlorite not only dissolves the pulpal and dentinal tissue but also acts as a potent antimicrobial agent.3 It is well recognized to be effective against a broad range of pathogens: gram-positive and gramnegative bacteria, fungi, spores, and viruses including the human immunodeficiency virus.10 NaOCl, especially when used in high concentrations, is known to be effective in dissolving organic tissue remnants and disinfecting the canal system.4 Effective concentrations of NaOCl range from 2.6% o 5.25%. The dilution of NaOCl was suggested because it has been proved that concentrations over 0.5% are cytotoxic.11 Compared with a chlorhexidine gel, NaOCl not only has a higher capacity to kill microorganisms but is also more able to remove cells from the root canal.12 Water is not effective in removing dentine debris from grooves in the apical portion of root canals.13
Disadvantages of NaOCl
Acute inflammation followed by necrosis results when NaOCl comes into contact with vital tissue. It causes severe inflammation and cellular...