Subgroup A: Er,Cr:YSGG laser
The root canals were filled with NaOCI solution and activated using Er, Cr: YSGG laser (Waterlase MD, Biolase Technology Inc., San Clemente, CA, USA) with an RFT2 tip. The tip, with a diameter of 275 microns in diameter and a length of 21 mm, was placed 1 mm short of the working length. The laser parameters were set to an output power of 2W, pulse frequency of 20 Hz, and a combination of 10% air and 10% water. The laser activation was performed in a slow and helical motion from the apical area to the coronal area for 8 s. The tip was positioned away from the dentinal walls and activated for 8 s, followed by a 10-s of deactivation period. This activation procedure was repeated 3 times, using fresh NaOCl solution for each cycle.