Research Article: Quantification by SIFT-MS of volatile compounds produced by the action of sodium hypochlorite on a model system of infected root canal content

Date Published: September 10, 2018

Publisher: Public Library of Science

Author(s): Konstantinos Ioannidis, Sadia Niazi, Sanjukta Deb, Francesco Mannocci, David Smith, Claire Turner, Chun-Pin Lin.


Root canal irrigation with sodium hypochlorite (NaOCl) is an indispensable part of the chemomechanical preparation of infected root canals in Endodontology. However, there is limited information on the emergence of toxic or hazardous volatile compounds (VOCs) from the interaction of NaOCl with the infected content of tooth biomaterials. The aim of this study was to assess the formation of VOCs and disinfection by-products (DBPs) following the interaction of NaOCl 2.5% v/v with a model system of different sources of natural organic matter (NOM) present in infected root canals, including dentine powder, planktonic multi-microbial suspensions (Propionibacterium acnes, Staphylococcus epidermidis, Actinomyces radicidentis, Streptococcus mitis and Enterococcus faecalis strain OMGS3202), bovine serum albumin 4%w/v and their combination. NaOCl was obtained from a stock solution with iodometric titration. Ultrapure water served as negative control. Samples were stirred at 37°C in aerobic and anaerobic conditions for 30min to approximate a clinically realistic time. Centrifugation was performed and the supernatants were collected and stored at -800 C until analysis. The reaction products were analysed in real time by selected ion flow tube mass spectrometry (SIFT-MS) in triplicates. SIFT-MS analysis showed that the released VOCs included chlorinated hydrocarbons, particularly chloroform, together with unexpected higher levels of some nitrogenous compounds, especially acetonitrile. No difference was observed between aerobic and anaerobic conditions. The chemical interaction of NaOCl with NOM resulted in the formation of toxic chlorinated VOCs and DBPs. SIFT-MS analysis proved to be an effective analytical method. The risks from the rise of toxic compounds require further consideration in dentistry.

Partial Text

Sodium hypochlorite (NaOCl) is one of the of the most widely practised public health components of disinfection of drinking water, sewage-water plants, water supply and distribution systems, swimming pools and industrial applications with the aim of preventing the spread of infection and contamination [1, 2]. Chlorination can kill the majority of bacteria, viruses and parasites responsible for waterborne diseases [3], as a strategy to meet the drinking water quality standards and disinfect waste water [4, 5]. Despite the importance of water disinfection, potentially harmful halogenated disinfection by-products (DBPs) can result from the reaction of chlorine or hypochlorite (which forms hypochlorous acid in water) with natural organic matter (NOM) in water, having negative health effects [6–8].

SIFT-MS is shown to be an effective technique for the real-time analysis of volatile compounds released by the reaction of NaOCl and representative components of an infected root canal system. Within the limitations of this ex vivo study and in the rejection of the null hypothesis, the chemical interaction of NaOCl 2.5% with dentine powder, bacteria, bovine serum albumin and their combination resulted in the formation of toxic DBPs and VOCs under both aerobic and anaerobic conditions.




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