Antioxidant and pro-oxidant properties of chlorhexidine and its interaction with calcium hydroxide solutions.

AIM: To evaluate the antioxidant and pro-oxidant properties of chlorhexidine (CHX). METHODOLOGY: The scavenging and generation of reactive oxygen species (ROS) by CHX in the presence or absence of saturated Ca(OH)(2) solutions was evaluated. The reaction emitted chemiluminescence in the presence of lucigenin thus was determined by a luminometer to evaluate the levels of ROS production. Changes in DNA conformation were analysed by agarose gel electrophoresis. Paired Student's t-test was used to compare the difference between groups. RESULTS: Chlorhexidine (0.00002-0.02%) effectively scavenged 56-88% of the superoxide radicals generated by the xanthine/xanthine oxidase reaction. Through analysis of PUC18 DNA conformation changes, CHX was shown to be a mild scavenger of hydroxyl radicals generated by H(2)O(2) plus FeCl(2). However, CHX (>0.083%) decreased the mobility of PUC18 plasmid DNA with potential production of DNA-DNA cross-link and severe DNA breaks (presence of DNA smear) at further higher concentrations. Furthermore, CHX induced ROS production including H(2)O(2) and superoxide radicals in 0.1N NaOH (pH = 12.76) or Ca(OH)(2) (pH = 12.5) solutions. CONCLUSION: Chlorhexidine exhibited both antioxidant and pro-oxidant properties under different conditions. These events are possibly involved in the killing of root canal and periodontal microorganisms when CHX and Ca(OH)(2) were used in combination or separately. Potential genotoxicity and tissue damage when extruded into the periradicular tissue and at higher concentrations should be considered during periodontal and endodontic practice.