Evaluation of active chlorine releasing of sodium hypochlorite during seven days, stored at different temperatures

The sanitation of the canal system through irrigation/aspiration, at the changing of the endodontic instruments aims to the excised material, removal of microorganisms and the cleaning of the walls of the canals. One of the substances used in endodontic treatment of root canals, sodium hypochlorite, used at different concentrations of active chlorine and pH, has gained popularity due to its physical chemical properties. Objective: To analyze the active chlorine content of sodium hypochlorite solution at 6.0%. Material and methods: 80 samples were obtained from two litres of sodium hypochlorite at 6%, obtained at every hour: one liter was stored at room temperature and one liter at refrigerated environment, between the morning and afternoon shifts, except on Saturday and Sunday. The free residual chlorine was determined, using as variables: the temperature, length of time in storage and the handling of the substance in the Endodontic clinic for seven days. The data obtained were submitted to analysis of variance according to the linear regression model to test the effect of time of storage condition and interaction between the main effects on the chlorine content of the stocked solution (p < 0.01). Results: The results showed that the sodium hypochlorite solution is quite unstable, with considerable loss of active chlorine (58.33%), depending on the storage conditions and storage time and temperature. The temperature interferes in the free residual chlorine concentration contained in sodium hypochlorite solution, that is, the higher the temperature, the lower the lifetime of free residual chlorine in sodium hypochlorite solutions. Conclusion: Storage in refrigerated environment proved to be the best option to avoid the marked loss of active chlorine in sodium hypochlorite of concentration at 6%.