The effect of temperature on the stability of sodium hypochlorite in a continuous chelation mixture containing the chelator clodronate.

This study evaluated the stability of continuous chelation mixtures of clodronate admixed with sodium hypochlorite at room temperature (23°C), at root canal temperature (34-35°C) and in refrigerated storage (2-4°C). In continuous chelation, one solution containing a chelator and sodium hypochlorite simultaneously disinfects and removes organic matter and smear layer. This technique is thought to enhance antimicrobial action and debris removal. However, hypochlorite stability and free available chlorine (FAC) levels may decline with elevated temperature and through chemical interactions with the chelator, thus reducing the therapeutic window of these mixtures. Employing iodometric titration, the FAC for clodronate-hypochlorite mixtures was measured at 34-35°C, 23°C and 2-4°C. Clodronate-hypochlorite solutions were stable for 180 min at 34-35°C. When kept at 2-4°C over 3 months, they maintain 95% of the FAC compared with baseline. It was concluded that the therapeutic window of clodronate-hypochlorite mixtures is unaffected at root canal temperature.