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J Conserv Dent. 2019 Jan-Feb;22(1):40-47. doi: 10.4103/JCD.JCD_284_18.

Qualitative and quantitative analysis of precipitate formation following interaction of chlorhexidine with sodium hypochlorite, neem, and tulsi.

Author information

Department of Conservative Dentistry and Endodontics, Saveetha Dental College, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India.



The interaction between chlorhexidine (CHX) and sodium hypochlorite (NaOCl) yields a thick precipitate capable of occluding dentinal tubules. Previous studies are unclear as to the above-mentioned precipitate contains para-chloroaniline (PCA) or not. PCA is a known toxic and carcinogenic compound which may lead to methemoglobinemia in humans.


This study aims to evaluate the precipitate formed on combination of different irrigants, weigh the amount of precipitate formed and to analyze the precipitate for PCA by using thin layer chromatography (TLC), high performance liquid chromatography (HPLC), column chromatography (CC), electron spray ionization mass spectrometry (ESI-MS), Ultraviolet (UV), and nuclear magnetic resonance (1H-NMR and C-13 NMR).

Materials and Methods:

Four different irrigants namely 2% CHX gluconate, 3% NaOCl, 5% neem and 5% tulsi were taken in different test tubes. Group 1, 2 and 3 included 1 ml 2% CHX combined with 1 ml each of 3% NaOCl, 5% neem and 5% tulsi. Group 4 and 5 comprised of 1 ml 3% NaOCl in combination with 1 ml 5% each of neem and tulsi. Finally, group 6 constituted 1 ml 5% neem mixed with 1 ml 5% tulsi. Each group was observed for 2 min for the formation of any precipitate, and the formed precipitate was weighed and analyzed using 1H-NMR and C-13 NMR, TLC, CC, HPLC, ESI-MS, and UV.

Statistical Analysis:

One-way ANOVA and Post hoc-Tukey test were used.


Presence of PCA was detected in group 1 (CHX + NaOCl), group 2 (CHX + neem) and group 3 (CHX + tusli) in all the sensitive methods employed.


The presence of PCA in precipitate was confirmed by TLC, CC, HPLC, ESI-MS, and UV. Based on the results of the present study, we assume that components in CHX are responsible for precipitate formation which contains PCA as well. Extrusion of precipitate beyond the apex may cause periapical tissue damage and delay wound healing at the same time.


Chlorhexidine; electron spray ionization mass spectrometry; high-performance liquid chromatography; neem extract; nuclear magnetic resonance; sodium hypochlorite; thin layer chromatography; tulsi extract and ultraviolet

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