Evaluation of the effect of different irrigation activation techniques on the penetration of irrigation solution into dentinal tubules by confocal laser scanning microscopic analysis

The aim of this study was to evaluate the efficacy of different irrigation techniques including standard needle irrigation (SNI), passive ultrasonic irrigation (PUI), endoactivator (EA), XP-Endo Finisher (XPF), photon-induced photoacoustic streaming (PIPS) and shockwave enhanced emission photoacoustic streaming (SWEEPS) systems on the penetration of irrigation solutions into dentinal tubules in teeth with oval canal shape applied with calcium hydroxide (Ca(OH)2) by confocal laser scanning microscope (CLSM). 90 mandibular uniradicular incisor teeth with oval shaped root canals were included in the current study. After the preparation of teeth up to Resiproc Blue R25 (VDW, Munich, Germany) the main canal was filled with a paste based on Ca(OH)2. Then the teeth were stored in 100% humidity at a temperature of 37°C for 14 days. Afterwards, the teeth were divided into six groups (n=15) according to the irrigation activation systems: SNI, PUI, EA, XPF, PIPS ve SWEEPS. In each group, 3 irrigation / activation cycles of 20 seconds of irrigation and 20 seconds of activation were performed with the relevant activation method. The root canals were filled with fluoroscein sodium (Sigma, AlldrichCo. St Louis, MO, USA) and activated with relevant activation method for 30 seconds. Specimens were sectioned horizontally to 1 ± 0.1 mm at 2., 5. and 8. mm from the apex and then examined under the CLSM. Maximum penetration depth, maximum penetration area and penetration percentage were measured by using Image J software. Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's post hoc tests (P = 0.05). No difference was found between the activation systems in terms of maximum penetration depth and maximum penetration area of irrigation solutions in the apical section (p>0.05). The penetration percentage of irrigation solutions was higher in PUI and PIPS compared to EA and XPF at the apical section (p<0.05). No difference was found between SNI, PUI, PIPS and SWEEPS in terms of penetration percentage of irrigation solutions in all sections (p>0.05). The penetration percentage of irrigation solutions was higher in the middle and coronal sections compared to the apical section in EA and XPF (p<0.05). Keywords: CLSM, irrigation activation systems, oval shaped root canals, PIPS, SWEEPS