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Title The Interaction of Sodium Hypochlorite and Chlorhexidine Gluconate, Two Commonly Used Endodontic Irrigants, Forms a Potentially Harmful Precipitate That Causes Obliteration of the Dentinal Tubules and Discoloration of the Root Canal System
Clinical Question Does the interaction of sodium hypochlorite (NaOCl) and chlorhexidine gluconate (CHX) form a harmful precipitate in large enough amounts to cause patient concern?
Clinical Bottom Line Sodium hypochlorite and chlorhexidine gluconate combine to form a dark brown precipitate containing small amounts of para-chloroanaline (PCA). PCA has been shown to be carcinogenic in rats and mice, and its precipitate causes occlusion of the dentinal tubules, which compromises the permeability of the tubules to sealer and gutta-percha. Irrigation with ethanol between the use of NaOCl and CHX eliminates the formation of this precipitate.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 18215677Bui/200844 single-rooted, extracted human teethLaboratory study
Key resultsExtracted teeth that were irrigated with both NaOCl and CHX had significantly fewer patent tubules (P<0.05) due to obliteration of the dentinal tubules by the precipitate formed from this reaction. Furthermore, the precipitate resulting from the interaction, which likely contained PCA, stained the walls of the root canal and therefore may lessen the effectiveness of the seal of the root canal treatment.
#2) 25305239Kolosowski/201412 dentin blocksLaboratory study
Key resultsTwelve dentin blocks were treated with both NaOCL and CHX and then analyzed using mass spectrometry to determine the exact composition of the byproduct, which was determined to contain breakdown products of CHX and PCA. The study found that rinsing with ethanol and distilled water between the NaOCL and CHX completely eliminates the formation of this precipitate.
#3) 2010141Chhabra/1990Mice and rats given varying levels of PCALaboratory study
Key resultsPCA was determined to be carcinogenic in male rats due to significantly greater incidences of sarcomas of the spleen and pheochromocytomas of the adrenal medulla, as well as hepatocellular neoplasms (p<0.05).
#4) 18215677Thomas/2010NMR analysis of reaction between CHXa and NaOClIn Vitro Study
Key resultsThe reaction of NaOCl with CHXa produces a dark brown precipitate, yet NMR spectroscopy shows no evidence of a measurable quantity of PCA in this precipitate.
Evidence Search (("Sodium Hypochlorite"[Mesh]) AND) AND "Chlorhexidine"[Mesh]
Comments on
The Evidence
There have not yet been any studies published on PCA's carcinogenicity in humans, but multiple studies have shown that it is carcinogenic in mice and rats. The in vitro laboratory studies conducted so far have all shown conflicting evidence as to whether PCA is found in the precipitate. However, this precipitate is still undesirable due to its occlusion of the dentinal tubules and the subsequent discoloration it causes. In vitro studies are difficult to generalize to clinical situations, but these studies do raise enough concerns to show that the use of NaOCl with CHX is questionable in humans. In terms of PCA's carcinogenicity to humans, it has been shown to cause cancer in mice and rats but these animals are exposed to far greater substance levels than humans. Further research must be done to see if this amount is cause for concern in humans.
Applicability These findings are applicable to any practitioner performing non-surgical root canal treatments, as chlorhexidine and sodium hypochlorite are both commonly used irrigants. Regardless of the identity of the precipitate formed from NaOCl and CHX, the dentist following this irrigation protocol needs to be aware that it can result in diminished dentinal permeability and an inadequate seal of the root canal treatment.
Specialty/Discipline (Endodontics) (General Dentistry)
Keywords p-chloroaniline, sodium hypochlorite, chlorhexidine gluconate, root canal irrigants
ID# 2907
Date of submission: 06/29/2015spacer
E-mail faltys@livemail.uthscsa.edu
Author David Quaid Faltys
Co-author(s) e-mail
Faculty mentor/Co-author Luis C. Yepes, DDS
Faculty mentor/Co-author e-mail yepes@uthscsa.edu
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