This study aimed to evaluate the effects of different irrigation activation techniques on root canal sealer penetration during non-surgical root canal retreatment and to determine which sealer type demonstrated greater penetrability into dentinal tubules. Instrumented root canals were allocated to a control group (needle technique) and three experimental groups: sonic activation (EDDY), passive ultrasonic irrigation (PUI), and Laser. The canals were obturated using AH+ and Totalfill BC Hiflow (BC) sealers. Retreatment was performed, and after 2 weeks, three sections from the apex at 3-, 8-, and 12-mm levels were examined using a confocal laser scanning microscope (CLSM) to investigate secondary sealer penetration. A three-way ANOVA followed by a post hoc test was used to analyze penetration depth and percentage. The BC sealer showed a marked difference in penetration depth and percentage compared with the AH+ sealer. The maximum penetration depth was observed in the middle region, where Laser and EDDY activation showed higher penetration depth and percentage values. PUI activation showed the lowest percentage of AH+ sealer penetration. Variations in results were observed in the coronal and apical regions; however, the differences were statistically nonsignificant. The use of Laser and EDDY for irrigation activation is promising in terms of tubule penetration of sealers, and Totalfill BC sealer showed better results than AH plus.
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