Objective: To evaluate the safety of sodium hypochlorite (NaOCl) irrigation using three different techniques during the final rinse in overinstrumented root canals.
Background data: The effect of irrigant activation on irrigant extrusion from overinstrumented root canals is still unclear.
Methods: A total of 30 single-rooted teeth were decoronated. The working lengths were determined and the roots were divided into two groups of 15 teeth each: group 1, instrumentation 0.5 mm short of the apical foramen and group 2, instrumentation 0.5 mm beyond the apical foramen (overinstrumented). Needle irrigation (NI), sonic irrigation with EndoActivator (EAI), and laser-activated irrigation (LAI) were used for the final rinse in each group; each root underwent the three irrigation procedures in a randomized crossover manner. A modified container-foam model was used to collect apically extruded NaOCl. The weight of the extruded NaOCl was calculated by subtracting the initial weights of the containers from their final weights. All data were statistically analyzed.
Results: The amount of NaOCl extrusion was similar with all three irrigation systems in group 1. In group 2, the amount of extruded NaOCl was significantly greater with EAI than with NI and LAI. EAI and LAI caused significantly greater extrusion in group 2 than in group 1.
Conclusions: EAI, NI, and LAI are equally safe for irrigating canals with intact apices. However, the risk of irrigant extrusion can increase in overinstrumented canals, with EAI associated with a greater risk compared with NI and LAI.
Keywords: EndoActivator; apical extrusion; irrigant agitation; laser-activated irrigation; overinstrumentation; sodium hypochlorite.