Apical extrusion of sodium hypochlorite using different root canal irrigation systems

Introduction: Root canal irrigation carries a risk of extrusion of irrigant into the periapical tissues. The objective of this study was to compare different irrigation systems in matched pairs of teeth prepared to an apical size of 35.06 and 50.06 by measuring the frequency and extent of apical extrusion of sodium hypochlorite (NaOCl) into a simulated periapical environment. The null hypothesis was tested that there is no difference between systems. Methods: Bilaterally matched pairs (n = 10) of single-canal extracted human anterior teeth were instrumented to an apical size of either 35.06 or 50.06. Teeth were embedded in a gel containing the pH-sensitive dye M-cresol purple that changes from yellow at pH 7.4 to purple at pH 9. Root canals were irrigated with 6% NaOCl (pH 11) by using EndoActivator (EA), EndoVac (EV), Rispi-Sonic/MicroMega 1500 (MM), passive ultrasonic irrigation (PUI), and syringe irrigation with a slot-tipped needle (SN), so that each tooth underwent all irrigation procedures in a randomized crossover design. Apical extrusion was evaluated by image analyses. Results: The frequency of extrusion was less in teeth with apical preparation size 35.06 (36%) compared with 50.06 (60%) (P =.014) and was dependent on the irrigation system in 35.06 (P =.039) but not 50.06 groups. In the 35.06 group the frequency of extrusion was less for EV than for MM and SN (both P =.029). The extent of extrusion was less for MM compared with PUI (P = .024) and SN (P =.046) in the 35.06 group and greater for SN compared with all other systems in the 50.06 group (P <.05). The null hypothesis was rejected. Conclusions: The frequency of apical extrusion of NaOCl was dependent on the type of root canal irrigation system and apical preparation size. The extent of extrusion depended on the irrigation system, with syringe and slotted-needle irrigation resulting in the greatest extent of extrusion.