The samples were randomly divided into four groups of 42 teeth each (), according to the treatment employed before obturation. The specimens in Group GØ received no laser treatment and served as control teeth. Teeth in Group Neodymium had the root canals irradiated with a 1064-nm Nd:YAG laser (Pulse Master 1000; American Dental Technologies, Southfield, Michigan) operated at 1.5 W, 100 mJ, 15 Hz, and , in pulsed mode.9,11,16 Group diode was irradiated with an 808-nm diode laser (Zap Softlase; Zap Lasers Ltd., Pleasant Hill, California) with a setting of 2.5 W in continuous mode.5,6,19,20 In the fourth group (Erbium), the root canals were irradiated with a 2940 nm Er:YAG laser (KavoKey laser 2; KaVo Co., Biberach, Germany) operated at 1 W, 100 mJ, 10 Hz, and in pulsed mode.12,13,18 All laser treatments were carried out according to the manufacturer’s instructions. The roots treated with a laser contained sterile water and were irradiated four times with circular movements, from apex to crown at a speed of with a 20 s interval between applications. For that, a fiber optic tip was inserted into the root canal until it reached the working length. At this moment, the laser was activated, and the irradiation was performed as described. All power settings were checked using a power meter (model 841P, Newport Corp., Irvine, California) before and after each irradiation.