Group 7- Er:YAG laser-activated irrigation: The irrigation solution was activated with the same protocol as in Group 3, with the exception that an Er:YAG laser (Kavo Key 3+, KaVo, Biberach, Germany) with a 2940 nm wavelength for 1 min. was used with endodontic tips (a 28 mm long and diameter ISO 30) in place of a CanalBrush. Laser parameters were 1 W, 10 Hz, 100 mJ, and an energy density of 142.8 J/cm2. The laser tip was inserted into canal at 1 mm short of the WL. When the root canal irrigant dropped or vaporized, the canal space was filled with 2.5% NaOCl.