Efficacy of sonically, ultrasonically and laser‐activated irrigation in removing a biofilm‐mimicking hydrogel from an isthmus model

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To evaluate the efficacy of sonically, ultrasonically and laser-activated irrigation (LAI) in removing a biofilm-mimicking hydrogel from the isthmus in a root canal model. Transparent resin blocks containing two standardized root canals (apical diameter of 0.3mm, 6% taper, 16mm long, with a coronal reservoir) connected by an isthmus (0.15mm wide, 2mm high) were used as the test model. The isthmus was filled with a hydrogel-containing dentine debris. The canals were filled with irrigant, and the models were randomly assigned to the following activation groups (n=20): EndoActivator (EA), Eddy, ultrasonically activated irrigation (UAI) with an Irrisafe 25mm length, size 25 file and LAI with a 2940nm Er:YAG-laser (20Hz, 50μs, 20mJ, PIPS tip at the canal entrance). All protocols were executed for 3×20s. Needle irrigation (NI) with a 27G needle served as the control. Standardized images of the isthmus were taken before and after irrigation, and the amount of removed hydrogel was determined using image analysis software and compared across groups using Welch anova (P≤0.05). Hydrogel removal was greatest in the LAI group (90.2%) and was significantly greater than that with UAI, EA and NI (P≤0.014), but not significantly different from Eddy (P=0.498). Hydrogel removal with Eddy (85.9%) was significantly greater than that with NI and EA (P<0.05), but not significantly different from UAI (P=0.07). There was no significant difference between the NI and EA groups (P=1). Laser-activated irrigation and Eddy resulted in the greatest hydrogel removal and performed better than EA and UAI. The effect of LAI was also not dependent on deep intracanal tip placement.