Using Diazotization to Characterize the Effect of Heat or Sodium Hypochlorite on 2.0% Chlorhexidine

Introduction: The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) results in the formation of a precipitate. In a previous study, we demonstrated the formation of 4-chloraniline (PCA) in the precipitate in an amount directly related to the concentration of NaOCl used. Aims and Methods: The aim of the present study was to use a diazotization technique to confirm the presence of an aromatic amine (like PCA) in the NaOCl/CHX precipitate and also in the 2.0% CHX at different temperatures (37 degrees C and 45 degrees C). Results: The results corroborated the presence of the aromatic amine in the precipitate and in the CHX at 45 degrees C. Conclusions: Further investigations of the precipitate should address the bioavailability of PCA leaching out from dentin and its cytotoxicity. Until the precipitate is studied further, it would appear prudent to minimize its formation. (J Endod 2009;35:1296-1299)