Periapical pressures developed by nonbinding irrigation needles at various irrigation delivery rates.

Introduction: Injection of sodium hypochlorite (NaOCl) from the root canal into periapical tissues may result in a NaOCl incident. The purpose of this study was to examine the fluid pressure generated by canal cleansing devices at the apical interface, when the tip of the irrigation device was not binding to the canal walls.

Methods: Apical pressure was monitored in a closed-system root canal model, with NaOCl delivered by a syringe pump at 0.5-8 mL/min. Devices tested were VPro EndoSafe, Max-i-Probe, NaviTip, VPro StreamClean, and EndoVac Microcannula. Apical fluid pressure was recorded with a digital manometer (N = 20). The relationships between apical fluid pressure and fluid flow rate were modeled with polynomial regression and analyzed by using the Wald test.

Results: EndoVac Microcannula was the only device that was capable of delivering negative apical fluid pressures, in the range of -35 mm Hg, at all fluid flow rates. All other devices generated positive apical pressures that increased nonlinearly with increasing fluid flow rates. These 4 positive pressure delivery devices were capable of generating pressures that exceeded the human central venous pressure (5.88 mm Hg). VPro EndoSafe differed from the other positive pressure delivery devices in that it generated significantly higher positive pressures at all flow rates (P < .0083).

Conclusions: Positive apical irrigation pressures in excess of the central venous pressure may be generated by some canal cleansing devices when irrigants are delivered at flow rates higher than 1 mL/min, even when the irrigation needle is not wedged into the canal walls.