It is generally accepted in endodontic practice that sodium hypochlorite is the most suitable solution for irrigation of the root canal system. Normal household bleach is approximately 5.5% sodium hypochlorite solution, and this may be diluted with purified water up to five times to the operator s preference. Research has shown that the antibacterial effect is the same for a 0.5% and a 5.0% solution.However, the greater the dilution the less effective is the solution at dissolving organic debris in the root canal system.
Great vigilance is essential when using sodium hypochlorite, and practitioners must be aware of the risks and dangers involved in its use. Irrigation under pressure may force the solution through the apical foramen into the periradicular tissues, which may result in a rapid, painful and serious inflammatory response. The patient will be extremely distressed, and little can be done to relieve the situation which may take several days to resolve. Cases have also been reported where excess pressure on the syringe has resulted in the needle coming loose and hypochlorite spraying over the patient, operator and assistant. Protective goggles are essential for the patient and all staff. Clothing should also be protected. The defence societies have received claims from irate patients for damaged clothing following root canal treatment. The practitioner must have appropriate risk assessment procedures in place when such materials are incorporated into their clinical practice.
Chlorhexidine solution 0.2% has a similar antibacterial action, but will not dissolve the organic debris found in parts of the canal system inaccessible to hand instrumentation, such as lateral canals, fins and apical deltas. However, the substantivity associated with this irrigant means that it will adhere to dentine, thereby exhibiting a prolonged antibacterial activity. Although chlorhexidine may not be quite as effective as sodium hypochlorite, its use should not be dismissed.
Researchers are constantly seeking improved methods of cleaning root canals; reports have appeared recently relating to the use of electroactivated water as an irrigant,and the use of high frequency electric current. These and others may prove interesting developments in root canal preparation and irrigation.
EDTA paste (Ethylenediamine tetra-acetic acid) is a chelating agent which softens the dentine of the canal walls and greatly facilitates canal preparation (Fig 13). EDTA solution may be used as an irrigant at the end of the canal preparation phase to assist removal of the smear layer prior to placement of an intervisit dressing, or obturation.