Short-term storage stability of NaOCl solutions when combined with Dual Rinse HEDP

Abstract

Aim

To assess the stability of NaOCl solutions when combined with a novel product for clinical use, Dual Rinse HEDP, which contains etidronate (1-hydroxyethane 1,1-diphosphonate).

Methodology

Mixtures of NaOCl solutions with Dual Rinse HEDP were prepared so that they initially contained 5.0%, 2.5%, or 1.0% NaOCl, and always 9.0% of dissolved Dual Rinse HEDP powder per total weight. NaOCl solutions alone were used as controls. The stability of these solutions over 8 h was assessed in transparent borosilicate glass bottles at ambient temperature (23°C). Subsequently, the effects of heating (60°C) or storing the solutions at 5°C were studied in polypropylene syringes. NaOCl concentrations were measured by iodometric titration, i.e. free available chlorine contents. Experiments were performed in triplicates.

Results

In the glass bottles at 23°C, the 5.0% NaOCl/9.0% Dual Rinse HEDP solution lost 20% of the available chlorine after 1 h, whilst the corresponding 2.5% NaOCl and 1.0% NaOCl solutions retained this relative amount of available chlorine for 2 and 4 h, respectively. Results obtained in the glass bottles were similar to those achieved in the syringes. Heating of the NaOCl/Dual Rinse HEDP mixtures had a detrimental effect on available chlorine, with a complete loss after 1 h. In contrast, storing the NaOCl/Dual Rinse HEDP mixtures in a refrigerator at 5°C kept the available chlorine high for 7 h, with the expected loss after a further hour of storage at 23°C.

Conclusions

Initial NaOCl concentration and temperature both affected short-term storage stability of combined solutions containing Dual Rinse HEDP.

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