Effect of Passive Ultrasonic Irrigation on Apical Extrusion of Irrigating Solution Tamer Tasdemira Kursat Era Davut Celika Tahsin Yildirimb AbStRACt Objectives: To determine the influence of passive ultrasonic irrigation (PUI) on apical extrusion of irrigating solution. Methods: Twenty freshly extracted maxillary and mandibular incisors with single straight root canals were instrumented with ProTaper rotary files. During final irrigation, the root canals were filled with 2.5% sodium hypochlorite (NaOCl) solution and PUI was performed with a piezoelectronic unit. A stainless steel instrument (size 15) was inserted into the root canal and the irrigant was ultrasonically activated for one minute. This sequence was repeated three times, resulting in a total PUI time of three minutes. The volume of extruded irrigant was measured by Pipetman pipettes. The data were statistically analyzed with the Mann-Whitney U test. Results: The mean volume of apical extruded irrigant was 2.15 µL for the PUI group and 14 µL for the control group. The experimental group extruded significantly smaller amounts of irrigant than the control group (P<.05). Conclusions: The PUI procedure as a final irrigation was associated with less apical extrusion of the irrigating solution. (Eur J Dent 2008;2:198-203) Key words: Apical extrusion; Passive; Ultrasonic; Irrigation. INtRoduCtIoN Root canal irrigation plays an important role in the debridement and disinfection of the root canal system.1 The currently available evidence strongly favors NaOCl as the main endodontic a Department of Endodontics, School of Dentistry, Karadeniz Technical University, Trabzon, Turkey. b Department of Restorative Dentistry, School of Dentistry, Karadeniz Technical University, Trabzon, Turkey. Corresponding author: Dr. Kursat Er, Department of Endodontics, School of Dentistry, Karadeniz Technical University, 61080, Trabzon, Turkey. Phone: +90 462 3774735 Fax: +90 462 3253017 E-mail: kursater@ktu.edu.tr 198 European Journal of Dentistry irrigant.2 Several investigations have shown its antibacterial effectiveness and tissue dissolution capacity.3-5 However, NaOCl is tissue cytotoxic and, when it contacts vital tissues; it causes hemolysis and ulceration, inhibits neutrophile migration and damages endothelium and fibroblast cells.6 Current dental literature includes many case presentations that report the damage to periapical tissues caused by NaOCl extruded accidentally from the apical foramen.1,7-9 Therefore, the possibility of accidental extrusion of NaOCl solution beyond the apical constriction must be considered during root canal irrigation. The first use of ultrasonics in endodontic practice was described by Richman10. Martin